Learning JavaScript with MDN (call, apply, bind)

Learning JavaScript with MDN (call, apply, bind)

call, apply, bind

Object.prototype.toString()

检测 js 数据类型

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString

Object.prototype.toString({})
// "[object Object]"
Object.prototype.toString([])
// "[object Object]"
Object.prototype.toString(Symbol())
// "[object Object]"
Object.prototype.toString(BigInt(1n))
// "[object Object]"

call, apply, bind

相同点: call, apply, bind 都是改变 this 的指向!

不同点:

1. call 会立即执行, 参数列表(arg1, arg2, arg3, ...)

Object.prototype.toString.call([]);
// "[object Array]"
Object.prototype.toString.call(Symbol());
// "[object Symbol]"
Object.prototype.toString.call(BigInt(1n));
// "[object BigInt]"

1. apply 会立即执行，参数数组 ([arg1, arg2, arg3, ...])

Object.prototype.toString.apply([]);
// "[object Array]"
Object.prototype.toString.apply(Symbol());
// "[object Symbol]"
Object.prototype.toString.apply(BigInt(1n));
// "[object BigInt]"

1. bind 不会立即执行, 需要手动调用

Object.prototype.toString.bind([]);
// ƒ toString() { [native code] }
Object.prototype.toString.bind([])();
"[object Array]"
// "[object Array]"
Object.prototype.toString.bind(Symbol());
// ƒ toString() { [native code] }
Object.prototype.toString.bind(Symbol())();
// "[object Symbol]"
Object.prototype.toString.bind(BigInt(1n));
// ƒ toString() { [native code] }
Object.prototype.toString.bind(BigInt(1n))();
// "[object BigInt]"

refs

https://www.cnblogs.com/xgqfrms/p/9209381.html

https://www.cnblogs.com/xgqfrms/p/13019790.html

https://stackoverflow.com/questions/15455009/javascript-call-apply-vs-bind

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