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@@ -0,0 +1,1384 @@
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+## 细则
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+
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+* **使用两个空格**进行缩进。
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+
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+ eslint: [`indent`](http://eslint.org/docs/rules/indent)
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+
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+ ```js
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+ function hello (name) {
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+ console.log('hi', name)
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+ }
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+ ```
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+
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+* 除需要转义的情况外,**字符串统一使用单引号**。
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+
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+ eslint: [`quotes`](http://eslint.org/docs/rules/quotes)
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+
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+ ```js
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+ console.log('hello there')
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+ $("<div class='box'>")
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+ ```
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+
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+* **不要定义未使用的变量**。
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+
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+ eslint: [`no-unused-vars`](http://eslint.org/docs/rules/no-unused-vars)
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+
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+ ```js
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+ function myFunction () {
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+ var result = something() // ✗ avoid
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+ }
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+ ```
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+
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+* **关键字后面加空格**。
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+
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+ eslint: [`keyword-spacing`](http://eslint.org/docs/rules/keyword-spacing)
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+
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+ ```js
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+ if (condition) { ... } // ✓ ok
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+ if(condition) { ... } // ✗ avoid
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+ ```
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+
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+* **函数声明时括号与函数名间加空格**。
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+
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+ eslint: [`space-before-function-paren`](http://eslint.org/docs/rules/space-before-function-paren)
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+
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+ ```js
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+ function name (arg) { ... } // ✓ ok
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+ function name(arg) { ... } // ✗ avoid
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+
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+ run(function () { ... }) // ✓ ok
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+ run(function() { ... }) // ✗ avoid
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+ ```
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+
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+* **始终使用** `===` 替代 `==`。<br>
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+ 例外: `obj == null` 可以用来检查 `null || undefined`。
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+
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+ eslint: [`eqeqeq`](http://eslint.org/docs/rules/eqeqeq)
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+
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+ ```js
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+ if (name === 'John') // ✓ ok
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+ if (name == 'John') // ✗ avoid
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+ ```
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+
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+ ```js
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+ if (name !== 'John') // ✓ ok
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+ if (name != 'John') // ✗ avoid
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+ ```
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+
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+* **字符串拼接操作符 (Infix operators)** 之间要留空格。
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+
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+ eslint: [`space-infix-ops`](http://eslint.org/docs/rules/space-infix-ops)
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+
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+ ```js
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+ // ✓ ok
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+ var x = 2
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+ var message = 'hello, ' + name + '!'
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+ ```
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+
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+ ```js
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+ // ✗ avoid
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+ var x=2
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+ var message = 'hello, '+name+'!'
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+ ```
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+
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+* **逗号后面加空格**。
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+
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+ eslint: [`comma-spacing`](http://eslint.org/docs/rules/comma-spacing)
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+
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+ ```js
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+ // ✓ ok
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+ var list = [1, 2, 3, 4]
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+ function greet (name, options) { ... }
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+ ```
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+
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+ ```js
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+ // ✗ avoid
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+ var list = [1,2,3,4]
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+ function greet (name,options) { ... }
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+ ```
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+
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+* **else 关键字要与花括号**保持在同一行。
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+
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+ eslint: [`brace-style`](http://eslint.org/docs/rules/brace-style)
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+
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+ ```js
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+ // ✓ ok
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+ if (condition) {
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+ // ...
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+ } else {
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+ // ...
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+ }
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+ ```
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+
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+ ```js
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+ // ✗ avoid
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+ if (condition)
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+ {
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+ // ...
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+ }
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+ else
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+ {
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+ // ...
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+ }
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+ ```
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+
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+* **多行 if 语句的**的括号不能省。
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+
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+ eslint: [`curly`](http://eslint.org/docs/rules/curly)
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+
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+ ```js
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+ // ✓ ok
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+ if (options.quiet !== true) console.log('done')
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+ ```
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+
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+ ```js
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+ // ✓ ok
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+ if (options.quiet !== true) {
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+ console.log('done')
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+ }
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+ ```
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+
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+ ```js
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+ // ✗ avoid
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+ if (options.quiet !== true)
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+ console.log('done')
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+ ```
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+
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+* **不要丢掉**异常处理中`err`参数。
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+
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+ eslint: [`handle-callback-err`](http://eslint.org/docs/rules/handle-callback-err)
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+ ```js
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+ // ✓ ok
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+ run(function (err) {
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+ if (err) throw err
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+ window.alert('done')
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+ })
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+ ```
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+
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+ ```js
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+ // ✗ avoid
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+ run(function (err) {
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+ window.alert('done')
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+ })
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+ ```
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+
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+* **使用浏览器全局变量时加上** `window.` 前缀。<br>
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+ Exceptions are: `document`, `console` and `navigator`.
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+
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+ eslint: [`no-undef`](http://eslint.org/docs/rules/no-undef)
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+
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+ ```js
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+ window.alert('hi') // ✓ ok
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+ ```
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+
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+* **不允许有连续多行空行**。
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+
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+ eslint: [`no-multiple-empty-lines`](http://eslint.org/docs/rules/no-multiple-empty-lines)
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+
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+ ```js
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+ // ✓ ok
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+ var value = 'hello world'
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+ console.log(value)
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+ ```
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+
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+ ```js
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+ // ✗ avoid
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+ var value = 'hello world'
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+
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+
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+ console.log(value)
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+ ```
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+
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+* **对于三元运算符** `?` 和 `:` 与他们所负责的代码处于同一行
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+
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+ eslint: [`operator-linebreak`](http://eslint.org/docs/rules/operator-linebreak)
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+
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+ ```js
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+ // ✓ ok
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+ var location = env.development ? 'localhost' : 'www.api.com'
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+
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+ // ✓ ok
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+ var location = env.development
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+ ? 'localhost'
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+ : 'www.api.com'
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+
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+ // ✗ avoid
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+ var location = env.development ?
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+ 'localhost' :
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+ 'www.api.com'
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+ ```
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+
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+* **每个 var 关键字**单独声明一个变量。
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+
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+ eslint: [`one-var`](http://eslint.org/docs/rules/one-var)
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+
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+ ```js
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+ // ✓ ok
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+ var silent = true
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+ var verbose = true
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+
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+ // ✗ avoid
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+ var silent = true, verbose = true
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+
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+ // ✗ avoid
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+ var silent = true,
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+ verbose = true
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+ ```
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+
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+* **条件语句中赋值语句**使用括号包起来。这样使得代码更加清晰可读,而不会认为是将条件判断语句的全等号(`===`)错写成了等号(`=`)。
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+
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+ eslint: [`no-cond-assign`](http://eslint.org/docs/rules/no-cond-assign)
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+
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+ ```js
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+ // ✓ ok
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+ while ((m = text.match(expr))) {
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+ // ...
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+ }
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+
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+ // ✗ avoid
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+ while (m = text.match(expr)) {
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+ // ...
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+ }
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+ ```
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+
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+* **单行代码块两边加空格**。
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+
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+ eslint: [`block-spacing`](http://eslint.org/docs/rules/block-spacing)
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+
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+ ```js
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+ function foo () {return true} // ✗ avoid
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+ function foo () { return true } // ✓ ok
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+ ```
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+
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+* **对于变量和函数名统一使用驼峰命名法**。
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+
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+ eslint: [`camelcase`](http://eslint.org/docs/rules/camelcase)
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+
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+ ```js
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+ function my_function () { } // ✗ avoid
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+ function myFunction () { } // ✓ ok
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+
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+ var my_var = 'hello' // ✗ avoid
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+ var myVar = 'hello' // ✓ ok
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+ ```
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+
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+* **不允许有多余的行末逗号**。
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+
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+ eslint: [`comma-dangle`](http://eslint.org/docs/rules/comma-dangle)
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+
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+ ```js
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+ var obj = {
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+ message: 'hello', // ✗ avoid
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+ }
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+ ```
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+
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+* **始终将逗号置于行末**。
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+
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+ eslint: [`comma-style`](http://eslint.org/docs/rules/comma-style)
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+
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+ ```js
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+ var obj = {
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+ foo: 'foo'
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+ ,bar: 'bar' // ✗ avoid
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+ }
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+
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+ var obj = {
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+ foo: 'foo',
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+ bar: 'bar' // ✓ ok
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+ }
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+ ```
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+
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+* **点号操作符须与属性需在同一行**。
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+
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+ eslint: [`dot-location`](http://eslint.org/docs/rules/dot-location)
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+
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+ ```js
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+ console.
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+ log('hello') // ✗ avoid
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+
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+ console
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+ .log('hello') // ✓ ok
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+ ```
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+
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+* **文件末尾留一空行**。
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+
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+ eslint: [`eol-last`](http://eslint.org/docs/rules/eol-last)
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+
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+* **函数调用时标识符与括号间不留间隔**。
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+
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+ eslint: [`func-call-spacing`](http://eslint.org/docs/rules/func-call-spacing)
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+
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+ ```js
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+ console.log ('hello') // ✗ avoid
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+ console.log('hello') // ✓ ok
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+ ```
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+
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+* **键值对当中冒号与值之间要留空白**。
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+
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+ eslint: [`key-spacing`](http://eslint.org/docs/rules/key-spacing)
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+
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+ ```js
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+ var obj = { 'key' : 'value' } // ✗ avoid
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+ var obj = { 'key' :'value' } // ✗ avoid
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+ var obj = { 'key':'value' } // ✗ avoid
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+ var obj = { 'key': 'value' } // ✓ ok
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+ ```
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+
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+* **构造函数要以大写字母开头**。
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+
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+ eslint: [`new-cap`](http://eslint.org/docs/rules/new-cap)
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+
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+ ```js
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+ function animal () {}
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+ var dog = new animal() // ✗ avoid
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+
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+ function Animal () {}
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+ var dog = new Animal() // ✓ ok
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+ ```
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+
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+* **无参的构造函数调用时要带上括号**。
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+
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+ eslint: [`new-parens`](http://eslint.org/docs/rules/new-parens)
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+
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+ ```js
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+ function Animal () {}
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+ var dog = new Animal // ✗ avoid
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+ var dog = new Animal() // ✓ ok
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+ ```
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+
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+* **对象中定义了存值器,一定要对应的定义取值器**。
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+
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+ eslint: [`accessor-pairs`](http://eslint.org/docs/rules/accessor-pairs)
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+
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+ ```js
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+ var person = {
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+ set name (value) { // ✗ avoid
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+ this._name = value
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+ }
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+ }
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+
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+ var person = {
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+ set name (value) {
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+ this._name = value
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+ },
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+ get name () { // ✓ ok
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+ return this._name
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+ }
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+ }
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+ ```
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+
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+* **子类的构造器中一定要调用 `super`**
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+
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+ eslint: [`constructor-super`](http://eslint.org/docs/rules/constructor-super)
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+
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+ ```js
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+ class Dog {
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+ constructor () {
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+ super() // ✗ avoid
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+ }
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+ }
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+
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+ class Dog extends Mammal {
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+ constructor () {
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+ super() // ✓ ok
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+ }
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+ }
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+ ```
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+
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+* **使用数组字面量而不是构造器**。
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+
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+ eslint: [`no-array-constructor`](http://eslint.org/docs/rules/no-array-constructor)
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+
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+ ```js
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+ var nums = new Array(1, 2, 3) // ✗ avoid
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+ var nums = [1, 2, 3] // ✓ ok
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+ ```
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+
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+* **避免使用 `arguments.callee` 和 `arguments.caller`**。
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+
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+ eslint: [`no-caller`](http://eslint.org/docs/rules/no-caller)
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+
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+ ```js
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+ function foo (n) {
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+ if (n <= 0) return
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+
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+ arguments.callee(n - 1) // ✗ avoid
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+ }
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+
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+ function foo (n) {
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+ if (n <= 0) return
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+
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+ foo(n - 1)
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+ }
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+ ```
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+
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+* **避免对类名重新赋值**。
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+
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+ eslint: [`no-class-assign`](http://eslint.org/docs/rules/no-class-assign)
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+
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+ ```js
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+ class Dog {}
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+ Dog = 'Fido' // ✗ avoid
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+ ```
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+
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+* **避免修改使用 `const` 声明的变量**。
|
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+
|
|
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+ eslint: [`no-const-assign`](http://eslint.org/docs/rules/no-const-assign)
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|
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+
|
|
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+ ```js
|
|
|
+ const score = 100
|
|
|
+ score = 125 // ✗ avoid
|
|
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+ ```
|
|
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+
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|
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+* **避免使用常量作为条件表达式的条件(循环语句除外)**。
|
|
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+
|
|
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+ eslint: [`no-constant-condition`](http://eslint.org/docs/rules/no-constant-condition)
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+
|
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+ ```js
|
|
|
+ if (false) { // ✗ avoid
|
|
|
+ // ...
|
|
|
+ }
|
|
|
+
|
|
|
+ if (x === 0) { // ✓ ok
|
|
|
+ // ...
|
|
|
+ }
|
|
|
+
|
|
|
+ while (true) { // ✓ ok
|
|
|
+ // ...
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **正则中不要使用控制符**。
|
|
|
+
|
|
|
+ eslint: [`no-control-regex`](http://eslint.org/docs/rules/no-control-regex)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ var pattern = /\x1f/ // ✗ avoid
|
|
|
+ var pattern = /\x20/ // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要使用 `debugger`**。
|
|
|
+
|
|
|
+ eslint: [`no-debugger`](http://eslint.org/docs/rules/no-debugger)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ function sum (a, b) {
|
|
|
+ debugger // ✗ avoid
|
|
|
+ return a + b
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要对变量使用 `delete` 操作**。
|
|
|
+
|
|
|
+ eslint: [`no-delete-var`](http://eslint.org/docs/rules/no-delete-var)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ var name
|
|
|
+ delete name // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要定义冗余的函数参数**。
|
|
|
+
|
|
|
+ eslint: [`no-dupe-args`](http://eslint.org/docs/rules/no-dupe-args)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ function sum (a, b, a) { // ✗ avoid
|
|
|
+ // ...
|
|
|
+ }
|
|
|
+
|
|
|
+ function sum (a, b, c) { // ✓ ok
|
|
|
+ // ...
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **类中不要定义冗余的属性**。
|
|
|
+
|
|
|
+ eslint: [`no-dupe-class-members`](http://eslint.org/docs/rules/no-dupe-class-members)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ class Dog {
|
|
|
+ bark () {}
|
|
|
+ bark () {} // ✗ avoid
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **对象字面量中不要定义重复的属性**。
|
|
|
+
|
|
|
+ eslint: [`no-dupe-keys`](http://eslint.org/docs/rules/no-dupe-keys)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ var user = {
|
|
|
+ name: 'Jane Doe',
|
|
|
+ name: 'John Doe' // ✗ avoid
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **`switch` 语句中不要定义重复的 `case` 分支**。
|
|
|
+
|
|
|
+ eslint: [`no-duplicate-case`](http://eslint.org/docs/rules/no-duplicate-case)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ switch (id) {
|
|
|
+ case 1:
|
|
|
+ // ...
|
|
|
+ case 1: // ✗ avoid
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **同一模块有多个导入时一次性写完**。
|
|
|
+
|
|
|
+ eslint: [`no-duplicate-imports`](http://eslint.org/docs/rules/no-duplicate-imports)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ import { myFunc1 } from 'module'
|
|
|
+ import { myFunc2 } from 'module' // ✗ avoid
|
|
|
+
|
|
|
+ import { myFunc1, myFunc2 } from 'module' // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **正则中不要使用空字符**。
|
|
|
+
|
|
|
+ eslint: [`no-empty-character-class`](http://eslint.org/docs/rules/no-empty-character-class)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const myRegex = /^abc[]/ // ✗ avoid
|
|
|
+ const myRegex = /^abc[a-z]/ // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要解构空值**。
|
|
|
+
|
|
|
+ eslint: [`no-empty-pattern`](http://eslint.org/docs/rules/no-empty-pattern)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const { a: {} } = foo // ✗ avoid
|
|
|
+ const { a: { b } } = foo // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要使用 `eval()`**。
|
|
|
+
|
|
|
+ eslint: [`no-eval`](http://eslint.org/docs/rules/no-eval)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ eval( "var result = user." + propName ) // ✗ avoid
|
|
|
+ var result = user[propName] // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **`catch` 中不要对错误重新赋值**。
|
|
|
+
|
|
|
+ eslint: [`no-ex-assign`](http://eslint.org/docs/rules/no-ex-assign)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ try {
|
|
|
+ // ...
|
|
|
+ } catch (e) {
|
|
|
+ e = 'new value' // ✗ avoid
|
|
|
+ }
|
|
|
+
|
|
|
+ try {
|
|
|
+ // ...
|
|
|
+ } catch (e) {
|
|
|
+ const newVal = 'new value' // ✓ ok
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要扩展原生对象**。
|
|
|
+
|
|
|
+ eslint: [`no-extend-native`](http://eslint.org/docs/rules/no-extend-native)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ Object.prototype.age = 21 // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **避免多余的函数上下文绑定**。
|
|
|
+
|
|
|
+ eslint: [`no-extra-bind`](http://eslint.org/docs/rules/no-extra-bind)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const name = function () {
|
|
|
+ getName()
|
|
|
+ }.bind(user) // ✗ avoid
|
|
|
+
|
|
|
+ const name = function () {
|
|
|
+ this.getName()
|
|
|
+ }.bind(user) // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **避免不必要的布尔转换**。
|
|
|
+
|
|
|
+ eslint: [`no-extra-boolean-cast`](http://eslint.org/docs/rules/no-extra-boolean-cast)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const result = true
|
|
|
+ if (!!result) { // ✗ avoid
|
|
|
+ // ...
|
|
|
+ }
|
|
|
+
|
|
|
+ const result = true
|
|
|
+ if (result) { // ✓ ok
|
|
|
+ // ...
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要使用多余的括号包裹函数**。
|
|
|
+
|
|
|
+ eslint: [`no-extra-parens`](http://eslint.org/docs/rules/no-extra-parens)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const myFunc = (function () { }) // ✗ avoid
|
|
|
+ const myFunc = function () { } // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **`switch` 一定要使用 `break` 来将条件分支正常中断**。
|
|
|
+
|
|
|
+ eslint: [`no-fallthrough`](http://eslint.org/docs/rules/no-fallthrough)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ switch (filter) {
|
|
|
+ case 1:
|
|
|
+ doSomething() // ✗ avoid
|
|
|
+ case 2:
|
|
|
+ doSomethingElse()
|
|
|
+ }
|
|
|
+
|
|
|
+ switch (filter) {
|
|
|
+ case 1:
|
|
|
+ doSomething()
|
|
|
+ break // ✓ ok
|
|
|
+ case 2:
|
|
|
+ doSomethingElse()
|
|
|
+ }
|
|
|
+
|
|
|
+ switch (filter) {
|
|
|
+ case 1:
|
|
|
+ doSomething()
|
|
|
+ // fallthrough // ✓ ok
|
|
|
+ case 2:
|
|
|
+ doSomethingElse()
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要省去小数点前面的0**。
|
|
|
+
|
|
|
+ eslint: [`no-floating-decimal`](http://eslint.org/docs/rules/no-floating-decimal)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const discount = .5 // ✗ avoid
|
|
|
+ const discount = 0.5 // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **避免对声明过的函数重新赋值**。
|
|
|
+
|
|
|
+ eslint: [`no-func-assign`](http://eslint.org/docs/rules/no-func-assign)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ function myFunc () { }
|
|
|
+ myFunc = myOtherFunc // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要对全局只读对象重新赋值**。
|
|
|
+
|
|
|
+ eslint: [`no-global-assign`](http://eslint.org/docs/rules/no-global-assign)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ window = {} // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **注意隐式的 `eval()`**。
|
|
|
+
|
|
|
+ eslint: [`no-implied-eval`](http://eslint.org/docs/rules/no-implied-eval)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ setTimeout("alert('Hello world')") // ✗ avoid
|
|
|
+ setTimeout(function () { alert('Hello world') }) // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **嵌套的代码块中禁止再定义函数**。
|
|
|
+
|
|
|
+ eslint: [`no-inner-declarations`](http://eslint.org/docs/rules/no-inner-declarations)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ if (authenticated) {
|
|
|
+ function setAuthUser () {} // ✗ avoid
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要向 `RegExp` 构造器传入非法的正则表达式**。
|
|
|
+
|
|
|
+ eslint: [`no-invalid-regexp`](http://eslint.org/docs/rules/no-invalid-regexp)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ RegExp('[a-z') // ✗ avoid
|
|
|
+ RegExp('[a-z]') // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要使用非法的空白符**。
|
|
|
+
|
|
|
+ eslint: [`no-irregular-whitespace`](http://eslint.org/docs/rules/no-irregular-whitespace)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ function myFunc () /*<NBSP>*/{} // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止使用 `__iterator__`**。
|
|
|
+
|
|
|
+ eslint: [`no-iterator`](http://eslint.org/docs/rules/no-iterator)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ Foo.prototype.__iterator__ = function () {} // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **外部变量不要与对象属性重名**。
|
|
|
+
|
|
|
+ eslint: [`no-label-var`](http://eslint.org/docs/rules/no-label-var)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ var score = 100
|
|
|
+ function game () {
|
|
|
+ score: while (true) { // ✗ avoid
|
|
|
+ score -= 10
|
|
|
+ if (score > 0) continue score
|
|
|
+ break
|
|
|
+ }
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要使用标签语句**。
|
|
|
+
|
|
|
+ eslint: [`no-labels`](http://eslint.org/docs/rules/no-labels)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ label:
|
|
|
+ while (true) {
|
|
|
+ break label // ✗ avoid
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要书写不必要的嵌套代码块**。
|
|
|
+
|
|
|
+ eslint: [`no-lone-blocks`](http://eslint.org/docs/rules/no-lone-blocks)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ function myFunc () {
|
|
|
+ { // ✗ avoid
|
|
|
+ myOtherFunc()
|
|
|
+ }
|
|
|
+ }
|
|
|
+
|
|
|
+ function myFunc () {
|
|
|
+ myOtherFunc() // ✓ ok
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要混合使用空格与制表符作为缩进**。
|
|
|
+
|
|
|
+ eslint: [`no-mixed-spaces-and-tabs`](http://eslint.org/docs/rules/no-mixed-spaces-and-tabs)
|
|
|
+
|
|
|
+* **除了缩进,不要使用多个空格**。
|
|
|
+
|
|
|
+ eslint: [`no-multi-spaces`](http://eslint.org/docs/rules/no-multi-spaces)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const id = 1234 // ✗ avoid
|
|
|
+ const id = 1234 // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要使用多行字符串**。
|
|
|
+
|
|
|
+ eslint: [`no-multi-str`](http://eslint.org/docs/rules/no-multi-str)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const message = 'Hello \
|
|
|
+ world' // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **`new` 创建对象实例后需要赋值给变量**。
|
|
|
+
|
|
|
+ eslint: [`no-new`](http://eslint.org/docs/rules/no-new)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ new Character() // ✗ avoid
|
|
|
+ const character = new Character() // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止使用 `Function` 构造器**。
|
|
|
+
|
|
|
+ eslint: [`no-new-func`](http://eslint.org/docs/rules/no-new-func)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ var sum = new Function('a', 'b', 'return a + b') // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止使用 `Object` 构造器**。
|
|
|
+
|
|
|
+ eslint: [`no-new-object`](http://eslint.org/docs/rules/no-new-object)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ let config = new Object() // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止使用 `new require`**。
|
|
|
+
|
|
|
+ eslint: [`no-new-require`](http://eslint.org/docs/rules/no-new-require)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const myModule = new require('my-module') // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止使用 `Symbol` 构造器**。
|
|
|
+
|
|
|
+ eslint: [`no-new-symbol`](http://eslint.org/docs/rules/no-new-symbol)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const foo = new Symbol('foo') // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止使用原始包装器**。
|
|
|
+
|
|
|
+ eslint: [`no-new-wrappers`](http://eslint.org/docs/rules/no-new-wrappers)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const message = new String('hello') // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要将全局对象的属性作为函数调用**。
|
|
|
+
|
|
|
+ eslint: [`no-obj-calls`](http://eslint.org/docs/rules/no-obj-calls)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const math = Math() // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要使用八进制字面量**。
|
|
|
+
|
|
|
+ eslint: [`no-octal`](http://eslint.org/docs/rules/no-octal)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const num = 042 // ✗ avoid
|
|
|
+ const num = '042' // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **字符串字面量中也不要使用八进制转义字符**。
|
|
|
+
|
|
|
+ eslint: [`no-octal-escape`](http://eslint.org/docs/rules/no-octal-escape)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const copyright = 'Copyright \251' // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **使用 `__dirname` 和 `__filename` 时尽量避免使用字符串拼接**。
|
|
|
+
|
|
|
+ eslint: [`no-path-concat`](http://eslint.org/docs/rules/no-path-concat)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const pathToFile = __dirname + '/app.js' // ✗ avoid
|
|
|
+ const pathToFile = path.join(__dirname, 'app.js') // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* 使用 `getPrototypeOf` 来替代 **`__proto__`**。
|
|
|
+
|
|
|
+ eslint: [`no-proto`](http://eslint.org/docs/rules/no-proto)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const foo = obj.__proto__ // ✗ avoid
|
|
|
+ const foo = Object.getPrototypeOf(obj) // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要重复声明变量**。
|
|
|
+
|
|
|
+ eslint: [`no-redeclare`](http://eslint.org/docs/rules/no-redeclare)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ let name = 'John'
|
|
|
+ let name = 'Jane' // ✗ avoid
|
|
|
+
|
|
|
+ let name = 'John'
|
|
|
+ name = 'Jane' // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **正则中避免使用多个空格**。
|
|
|
+
|
|
|
+ eslint: [`no-regex-spaces`](http://eslint.org/docs/rules/no-regex-spaces)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const regexp = /test value/ // ✗ avoid
|
|
|
+
|
|
|
+ const regexp = /test {3}value/ // ✓ ok
|
|
|
+ const regexp = /test value/ // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **return 语句中的赋值必需有括号包裹**。
|
|
|
+
|
|
|
+ eslint: [`no-return-assign`](http://eslint.org/docs/rules/no-return-assign)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ function sum (a, b) {
|
|
|
+ return result = a + b // ✗ avoid
|
|
|
+ }
|
|
|
+
|
|
|
+ function sum (a, b) {
|
|
|
+ return (result = a + b) // ✓ ok
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **避免将变量赋值给自己**。
|
|
|
+
|
|
|
+ eslint: [`no-self-assign`](http://eslint.org/docs/rules/no-self-assign)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ name = name // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **避免将变量与自己进行比较操作**。
|
|
|
+
|
|
|
+ esint: [`no-self-compare`](http://eslint.org/docs/rules/no-self-compare)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ if (score === score) {} // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **避免使用逗号操作符**。
|
|
|
+
|
|
|
+ eslint: [`no-sequences`](http://eslint.org/docs/rules/no-sequences)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ if (doSomething(), !!test) {} // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要随意更改关键字的值**。
|
|
|
+
|
|
|
+ eslint: [`no-shadow-restricted-names`](http://eslint.org/docs/rules/no-shadow-restricted-names)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ let undefined = 'value' // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止使用稀疏数组(Sparse arrays)**。
|
|
|
+
|
|
|
+ eslint: [`no-sparse-arrays`](http://eslint.org/docs/rules/no-sparse-arrays)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ let fruits = ['apple',, 'orange'] // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **不要使用制表符**。
|
|
|
+
|
|
|
+ eslint: [`no-tabs`](http://eslint.org/docs/rules/no-tabs)
|
|
|
+
|
|
|
+* **正确使用 ES6 中的字符串模板**。
|
|
|
+
|
|
|
+ eslint: [`no-template-curly-in-string`](http://eslint.org/docs/rules/no-template-curly-in-string)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const message = 'Hello ${name}' // ✗ avoid
|
|
|
+ const message = `Hello ${name}` // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **使用 `this` 前请确保 `super()` 已调用**。
|
|
|
+
|
|
|
+ eslint: [`no-this-before-super`](http://eslint.org/docs/rules/no-this-before-super)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ class Dog extends Animal {
|
|
|
+ constructor () {
|
|
|
+ this.legs = 4 // ✗ avoid
|
|
|
+ super()
|
|
|
+ }
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **用 `throw` 抛错时,抛出 `Error` 对象而不是字符串**。
|
|
|
+
|
|
|
+ eslint: [`no-throw-literal`](http://eslint.org/docs/rules/no-throw-literal)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ throw 'error' // ✗ avoid
|
|
|
+ throw new Error('error') // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **行末不留空格**。
|
|
|
+
|
|
|
+ eslint: [`no-trailing-spaces`](http://eslint.org/docs/rules/no-trailing-spaces)
|
|
|
+
|
|
|
+* **不要使用 `undefined` 来初始化变量**。
|
|
|
+
|
|
|
+ eslint: [`no-undef-init`](http://eslint.org/docs/rules/no-undef-init)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ let name = undefined // ✗ avoid
|
|
|
+
|
|
|
+ let name
|
|
|
+ name = 'value' // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **循环语句中注意更新循环变量**。
|
|
|
+
|
|
|
+ eslint: [`no-unmodified-loop-condition`](http://eslint.org/docs/rules/no-unmodified-loop-condition)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ for (let i = 0; i < items.length; j++) {...} // ✗ avoid
|
|
|
+ for (let i = 0; i < items.length; i++) {...} // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **如果有更好的实现,尽量不要使用三元表达式**。
|
|
|
+
|
|
|
+ eslint: [`no-unneeded-ternary`](http://eslint.org/docs/rules/no-unneeded-ternary)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ let score = val ? val : 0 // ✗ avoid
|
|
|
+ let score = val || 0 // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **`return`,`throw`,`continue` 和 `break` 后不要再跟代码**。
|
|
|
+
|
|
|
+ eslint: [`no-unreachable`](http://eslint.org/docs/rules/no-unreachable)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ function doSomething () {
|
|
|
+ return true
|
|
|
+ console.log('never called') // ✗ avoid
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **`finally` 代码块中不要再改变程序执行流程**。
|
|
|
+
|
|
|
+ eslint: [`no-unsafe-finally`](http://eslint.org/docs/rules/no-unsafe-finally)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ try {
|
|
|
+ // ...
|
|
|
+ } catch (e) {
|
|
|
+ // ...
|
|
|
+ } finally {
|
|
|
+ return 42 // ✗ avoid
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **关系运算符的左值不要做取反操作**。
|
|
|
+
|
|
|
+ eslint: [`no-unsafe-negation`](http://eslint.org/docs/rules/no-unsafe-negation)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ if (!key in obj) {} // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **避免不必要的 `.call()` 和 `.apply()`**。
|
|
|
+
|
|
|
+ eslint: [`no-useless-call`](http://eslint.org/docs/rules/no-useless-call)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ sum.call(null, 1, 2, 3) // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **避免使用不必要的计算值作对象属性**。
|
|
|
+
|
|
|
+ eslint: [`no-useless-computed-key`](http://eslint.org/docs/rules/no-useless-computed-key)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const user = { ['name']: 'John Doe' } // ✗ avoid
|
|
|
+ const user = { name: 'John Doe' } // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止多余的构造器**。
|
|
|
+
|
|
|
+ eslint: [`no-useless-constructor`](http://eslint.org/docs/rules/no-useless-constructor)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ class Car {
|
|
|
+ constructor () { // ✗ avoid
|
|
|
+ }
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止不必要的转义**。
|
|
|
+
|
|
|
+ eslint: [`no-useless-escape`](http://eslint.org/docs/rules/no-useless-escape)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ let message = 'Hell\o' // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **import, export 和解构操作中,禁止赋值到同名变量**。
|
|
|
+
|
|
|
+ eslint: [`no-useless-rename`](http://eslint.org/docs/rules/no-useless-rename)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ import { config as config } from './config' // ✗ avoid
|
|
|
+ import { config } from './config' // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **属性前面不要加空格**。
|
|
|
+
|
|
|
+ eslint: [`no-whitespace-before-property`](http://eslint.org/docs/rules/no-whitespace-before-property)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ user .name // ✗ avoid
|
|
|
+ user.name // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **禁止使用 `with`**。
|
|
|
+
|
|
|
+ eslint: [`no-with`](http://eslint.org/docs/rules/no-with)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ with (val) {...} // ✗ avoid
|
|
|
+ ```
|
|
|
+
|
|
|
+* **对象属性换行时注意统一代码风格**。
|
|
|
+
|
|
|
+ eslint: [`object-property-newline`](http://eslint.org/docs/rules/object-property-newline)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const user = {
|
|
|
+ name: 'Jane Doe', age: 30,
|
|
|
+ username: 'jdoe86' // ✗ avoid
|
|
|
+ }
|
|
|
+
|
|
|
+ const user = { name: 'Jane Doe', age: 30, username: 'jdoe86' } // ✓ ok
|
|
|
+
|
|
|
+ const user = {
|
|
|
+ name: 'Jane Doe',
|
|
|
+ age: 30,
|
|
|
+ username: 'jdoe86'
|
|
|
+ } // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **代码块中避免多余留白**。
|
|
|
+
|
|
|
+ eslint: [`padded-blocks`](http://eslint.org/docs/rules/padded-blocks)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ if (user) {
|
|
|
+ // ✗ avoid
|
|
|
+ const name = getName()
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ if (user) {
|
|
|
+ const name = getName() // ✓ ok
|
|
|
+ }
|
|
|
+ ```
|
|
|
+
|
|
|
+* **展开运算符与它的表达式间不要留空白**。
|
|
|
+
|
|
|
+ eslint: [`rest-spread-spacing`](http://eslint.org/docs/rules/rest-spread-spacing)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ fn(... args) // ✗ avoid
|
|
|
+ fn(...args) // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **遇到分号时空格要后留前不留**。
|
|
|
+
|
|
|
+ eslint: [`semi-spacing`](http://eslint.org/docs/rules/semi-spacing)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ for (let i = 0 ;i < items.length ;i++) {...} // ✗ avoid
|
|
|
+ for (let i = 0; i < items.length; i++) {...} // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **代码块首尾留空格**。
|
|
|
+
|
|
|
+ eslint: [`space-before-blocks`](http://eslint.org/docs/rules/space-before-blocks)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ if (admin){...} // ✗ avoid
|
|
|
+ if (admin) {...} // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **圆括号间不留空格**。
|
|
|
+
|
|
|
+ eslint: [`space-in-parens`](http://eslint.org/docs/rules/space-in-parens)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ getName( name ) // ✗ avoid
|
|
|
+ getName(name) // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **一元运算符后面跟一个空格**。
|
|
|
+
|
|
|
+ eslint: [`space-unary-ops`](http://eslint.org/docs/rules/space-unary-ops)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ typeof!admin // ✗ avoid
|
|
|
+ typeof !admin // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **注释首尾留空格**。
|
|
|
+
|
|
|
+ eslint: [`spaced-comment`](http://eslint.org/docs/rules/spaced-comment)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ //comment // ✗ avoid
|
|
|
+ // comment // ✓ ok
|
|
|
+
|
|
|
+ /*comment*/ // ✗ avoid
|
|
|
+ /* comment */ // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **模板字符串中变量前后不加空格**。
|
|
|
+
|
|
|
+ eslint: [`template-curly-spacing`](http://eslint.org/docs/rules/template-curly-spacing)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const message = `Hello, ${ name }` // ✗ avoid
|
|
|
+ const message = `Hello, ${name}` // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **检查 `NaN` 的正确姿势是使用 `isNaN()`**。
|
|
|
+
|
|
|
+ eslint: [`use-isnan`](http://eslint.org/docs/rules/use-isnan)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ if (price === NaN) { } // ✗ avoid
|
|
|
+ if (isNaN(price)) { } // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **用合法的字符串跟 `typeof` 进行比较操作**。
|
|
|
+
|
|
|
+ eslint: [`valid-typeof`](http://eslint.org/docs/rules/valid-typeof)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ typeof name === 'undefimed' // ✗ avoid
|
|
|
+ typeof name === 'undefined' // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **自调用匿名函数 (IIFEs) 使用括号包裹**。
|
|
|
+
|
|
|
+ eslint: [`wrap-iife`](http://eslint.org/docs/rules/wrap-iife)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ const getName = function () { }() // ✗ avoid
|
|
|
+
|
|
|
+ const getName = (function () { }()) // ✓ ok
|
|
|
+ const getName = (function () { })() // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **`yield *` 中的 `*` 前后都要有空格**。
|
|
|
+
|
|
|
+ eslint: [`yield-star-spacing`](http://eslint.org/docs/rules/yield-star-spacing)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ yield* increment() // ✗ avoid
|
|
|
+ yield * increment() // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+* **请书写优雅的条件语句(avoid Yoda conditions)**。
|
|
|
+
|
|
|
+ eslint: [`yoda`](http://eslint.org/docs/rules/yoda)
|
|
|
+
|
|
|
+ ```js
|
|
|
+ if (42 === age) { } // ✗ avoid
|
|
|
+ if (age === 42) { } // ✓ ok
|
|
|
+ ```
|
|
|
+
|
|
|
+## 关于分号
|
|
|
+
|
|
|
+* 不要使用分号。 (参见:[1](http://blog.izs.me/post/2353458699/an-open-letter-to-javascript-leaders-regarding),[2](http://inimino.org/%7Einimino/blog/javascript_semicolons),[3](https://www.youtube.com/watch?v=gsfbh17Ax9I))
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+
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+ eslint: [`semi`](http://eslint.org/docs/rules/semi)
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+
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+ ```js
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+ window.alert('hi') // ✓ ok
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+ window.alert('hi'); // ✗ avoid
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+ ```
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+
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+* 不要使用 `(`, `[`, or `` ` `` 等作为一行的开始。在没有分号的情况下代码压缩后会导致报错,而坚持这一规范则可避免出错。
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+
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+ eslint: [`no-unexpected-multiline`](http://eslint.org/docs/rules/no-unexpected-multiline)
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+
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+ ```js
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+ // ✓ ok
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+ ;(function () {
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+ window.alert('ok')
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+ }())
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+
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+ // ✗ avoid
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+ (function () {
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+ window.alert('ok')
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+ }())
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+ ```
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+
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+ ```js
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+ // ✓ ok
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+ ;[1, 2, 3].forEach(bar)
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+
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+ // ✗ avoid
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+ [1, 2, 3].forEach(bar)
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+ ```
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+
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+ ```js
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+ // ✓ ok
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+ ;`hello`.indexOf('o')
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+
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+ // ✗ avoid
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+ `hello`.indexOf('o')
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+ ```
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+
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+ 备注:上面的写法只能说聪明过头了。
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+
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+ 相比更加可读易懂的代码,那些看似投巧的写法是不可取的。
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+
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+ 譬如:
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+
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+ ```js
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+ ;[1, 2, 3].forEach(bar)
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+ ```
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+
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+ 建议的写法是:
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+
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+ ```js
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+ var nums = [1, 2, 3]
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+ nums.forEach(bar)
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+ ```
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+
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+
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+## 拓展阅读
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+
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+- [An Open Letter to JavaScript Leaders Regarding Semicolons][1]
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+- [JavaScript Semicolon Insertion – Everything you need to know][2]
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+
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+##### 一个值得观看的视频:
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+
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+- [JavaScript 中的分号多余吗?- YouTube][3]
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+
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+当前主流的代码压缩方案都是基于词法(AST-based)进行的,所以在处理无分号的代码时完全没有压力(何况 JavaScript 中分号本来就不是强制的)。
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+
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+##### 一段摘抄自 *["An Open Letter to JavaScript Leaders Regarding Semicolons"][1]* 这篇文章的内容:
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+
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+> [自动化插入分号的做法]是安全可依赖的,而且其产出的代码能够在所有浏览器里很好地运行。 Closure compiler, yuicompressor, packer 还有 jsmin 都能正确地对这样的代码进行压缩处理。并没有任何性能相关的问题。
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+>
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+> 不得不说,Javascript 社区里的大牛们一直是错误的,并不能教给你最佳实践。真是让人忧伤啊。 我建议先弄清楚 JS 是怎样断句的(还有就是哪些地方看起来断了其实并没有),明白了这个后就可以随心写出漂亮的代码了。
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+>
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+> 一般来说, `\n` 表示语句结束,除非:
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+> 1. 该语句有未闭合的括号, 数组字面量, 对象字面量 或者其他不能正常结束一条语句的情况(譬如,以 `.` 或 `,` 结尾)
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+> 2. 该语句是 `--` 或者 `++` (它会将后面的内容进行自增或减)
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+> 3. 该语句是 `for()`,`while()`,`do`,`if()` 或者 `else` 并且没有 `{`
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+> 4. 下一行以 `[`,`(`,`+`,`*`,`/`,`-`,`,`,`.` 或者其他只会单独出现在两块内容间的二元操作符。
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+>
|
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+> 第一条很容易理解。即使在 JSLint 中,也允许 JSON,构造器的括号中,以及使用 `var` 配合 `,` 结尾来声明多个变量等这些情中包含 `\n`。
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+>
|
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+> 第二条有点奇葩。 我还想不出谁会(除了这里用作讨论外)写出 `i\n++\nj` 这样的代码来,不过,顺便说一下,这种写法最后解析的结果是 `i; ++j`,而不是 `i++; j`。
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+>
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+> 第三条也容易理解。 `if (x)\ny()` 等价于 `if (x) { y() }`。解释器会向下寻找到代码块或一条语句为止。
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+>
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+> `;` 是条合法的 JavaScript 语句。所以 `if(x);` 等价于 `if(x){}`,表示 “如果 x 为真,什么也不做。” 这种写法在循环里面可以看到,就是当条件判断与条件更新是同一个方法的时候。 不常见,但也不至于没听说过吧。
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+>
|
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+> 第四条就是常见的 “看,说过要加分号!” 的情形。但这些情况可以通过在语句前面加上分号来解决,如果你确定该语句跟前面的没关系的话。举个例子,假如你想这样:
|
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+>
|
|
|
+> ```js
|
|
|
+> foo();
|
|
|
+> [1,2,3].forEach(bar);
|
|
|
+> ```
|
|
|
+>
|
|
|
+> 那么完全可以这样来写:
|
|
|
+>
|
|
|
+> ```js
|
|
|
+> foo()
|
|
|
+> ;[1,2,3].forEach(bar)
|
|
|
+> ```
|
|
|
+>
|
|
|
+> 后者的好处是分号比较瞩目,一旦习惯后便再也不会看到以 `(` 和 `[` 开头又不带分号的语句了。
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+
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+[1]: http://blog.izs.me/post/2353458699/an-open-letter-to-javascript-leaders-regarding
|
|
|
+[2]: http://inimino.org/~inimino/blog/javascript_semicolons
|
|
|
+[3]: https://www.youtube.com/watch?v=gsfbh17Ax9I
|