如何以编程方式区分箭头函数和常规函数？ [英] How to programmatically distinguish an arrow function from a regular function?

问题描述

箭头功能和常规功能。

({}).toString.call(function () {})
"[object Function]"
({}).toString.call(() => {})
"[object Function]"

或

console.dir( (function () {}) )

function anonymous()
    arguments: null
    caller: null
    length: 0
    name: ""
    prototype: Object
    __proto__: ()
    <function scope>

console.dir( (() => {}) )

function anonymous()
    arguments: (...)
    caller: (...)
    length: 0
    name: ""
    __proto__: ()
    <function scope>

两者的行为不同但有效用例能够区分两者。

The behaviour of the two is different though and there is a valid use case for being able to tell the two apart.

如何以编程方式区分箭头函数和常规函数？

How to programmatically distinguish an arrow function from a regular function?

推荐答案

我能想到的最好的就是使用 toString ：

The best I can think of is using toString:

let isArrowFunction;

isArrowFunction = (fn) => {
    console.log(fn.toString());

    return fn.toString().indexOf('function') !== 0;
};

console.log(isArrowFunction(() => {}) === true);
console.log(isArrowFunction((foo: string) => {}) === true);
console.log(isArrowFunction(function () {}) === false);

参见：

(function () {}).toString();
"function () {}"

(() => {}).toString();
"() => {}"

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