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// 1.在箭头函数里没有自己的 this 和 arguments
let a = {
foo: 42,
bar: () => {
// console.log(this);
// console.log(arguments); // 报错
console.log('Inside `bar`:', this.foo);
console.log('Inside `bar`:', a.foo);
/* Inside `bar`: undefined
Inside `bar`: 42 */
},
}
a.bar();
// 2.在匿名函数里有
let b = {
foo: 42,
bar: function() {
console.log(this); // {foo: 42, bar: ƒ}bar: ƒ ()foo: 42__proto__: Object
console.log(arguments); // Arguments [callee: ƒ, Symbol(Symbol.iterator): ƒ]callee: ƒ ()arguments: nullcaller: nulllength: 0name: "bar"prototype: {constructor: ƒ}__proto__: ƒ ()[[FunctionLocation]]: 箭头函数.html:27[[Scopes]]: Scopes[2]length: 0Symbol(Symbol.iterator): ƒ values()__proto__: Object
console.log('Inside `bar`:', this.foo); // Inside `bar`: 42
},
}
b.bar();
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箭头函数无法 new
- 箭头函数无法 new
> new (() => {});
TypeError: (intermediate value) is not a constructor
> var x = () => {};
> new x();
TypeError: x is not a constructor
- 匿名函数可以
> new (function() {});
{}
> let f = function() {};
> new f();
f {}