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:

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]"

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]"

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]"