prefer-arrow-callback
需要使用箭头函数进行回调
此规则报告的一些问题可通过 --fix 命令行选项自动修复
箭头函数可以成为回调或函数参数的函数表达式的有吸引力的替代方案。
¥Arrow functions can be an attractive alternative to function expressions for callbacks or function arguments.
例如，箭头函数会自动绑定到它们周围的范围/上下文。这为显式绑定函数表达式的 ES6 之前的标准提供了一种替代方法，以实现类似的行为。
¥For example, arrow functions are automatically bound to their surrounding scope/context. This provides an alternative to the pre-ES6 standard of explicitly binding function expressions to achieve similar behavior.
此外，箭头函数是：
¥Additionally, arrow functions are:
-
不那么冗长，更容易推断。
¥less verbose, and easier to reason about.
-
无论何时何地调用它们，都以词法方式绑定。
¥bound lexically regardless of where or when they are invoked.
规则详情
¥Rule Details
此规则定位用作回调或函数参数的函数表达式。任何可以被箭头函数替换而不改变结果的东西都会产生错误。
¥This rule locates function expressions used as callbacks or function arguments. An error will be produced for any that could be replaced by an arrow function without changing the result.
以下示例将被标记：
¥The following examples will be flagged:
/* eslint prefer-arrow-callback: "error" */
foo(function(a) { return a; }); // ERROR
// prefer: foo(a => a)
foo(function() { return this.a; }.bind(this)); // ERROR
// prefer: foo(() => this.a)
箭头函数不会产生相同结果的实例将被忽略。
¥Instances where an arrow function would not produce identical results will be ignored.
以下示例将不会被标记：
¥The following examples will not be flagged:
/* eslint prefer-arrow-callback: "error" */
// arrow function callback
foo(a => a); // OK
// generator as callback
foo(function*() { yield; }); // OK
// function expression not used as callback or function argument
var foo = function foo(a) { return a; }; // OK
// unbound function expression callback
foo(function() { return this.a; }); // OK
// recursive named function callback
foo(function bar(n) { return n && n + bar(n - 1); }); // OK
选项
¥Options
通过选项对象进一步控制此规则的行为。
¥Access further control over this rule’s behavior via an options object.
默认：{ allowNamedFunctions: false, allowUnboundThis: true }
¥Default: { allowNamedFunctions: false, allowUnboundThis: true }
allowNamedFunctions
默认情况下 { "allowNamedFunctions": false }，此 boolean 选项禁止使用命名函数作为回调或函数参数。
¥By default { "allowNamedFunctions": false }, this boolean option prohibits using named functions as callbacks or function arguments.
将此值更改为 true 将通过允许无限制地使用命名函数来反转此选项的行为。
¥Changing this value to true will reverse this option’s behavior by allowing use of named functions without restriction.
{ "allowNamedFunctions": true } 不会标记以下示例：
¥{ "allowNamedFunctions": true } will not flag the following example:
/* eslint prefer-arrow-callback: [ "error", { "allowNamedFunctions": true } ] */
foo(function bar() {});
allowUnboundThis
默认情况下 { "allowUnboundThis": true }，这个 boolean 选项允许包含 this 的函数表达式用作回调，只要有问题的函数没有被显式绑定。
¥By default { "allowUnboundThis": true }, this boolean option allows function expressions containing this to be used as callbacks, as long as the function in question has not been explicitly bound.
当设置为 false 时，此选项完全禁止将函数表达式用作回调或函数参数，无一例外。
¥When set to false this option prohibits the use of function expressions as callbacks or function arguments entirely, without exception.
{ "allowUnboundThis": false } 将标记以下示例：
¥{ "allowUnboundThis": false } will flag the following examples:
/* eslint prefer-arrow-callback: [ "error", { "allowUnboundThis": false } ] */
foo(function() { this.a; });
foo(function() { (() => this); });
someArray.map(function(item) { return this.doSomething(item); }, someObject);
何时不使用
¥When Not To Use It
-
在尚未采用 ES6 语言特性 (ES3/5) 的环境中。
¥In environments that have not yet adopted ES6 language features (ES3/5).
-
在描述回调或函数参数时允许使用函数表达式的 ES6+ 环境中。
¥In ES6+ environments that allow the use of function expressions when describing callbacks or function arguments.
版本
此规则是在 ESLint v1.2.0 中引入。