javascript - 混淆javascript绑定(bind)函数

Question

我运行下面的 JS 脚本，但只发现 func2() 输出是 foobar，而不是 George，谁能解释为什么 func2 = func.bind(someuser) 没有将 someuser 绑定(bind)到 func 吗？

var someuser = {
    name: 'George',
    func: function () {
        console.log(this.name);
    }
};
var foo = {
    name: 'foobar'
};
func = someuser.func.bind(foo);
func(); // output foobar
func2 = func.bind(someuser);
func2(); //output foobar

Answer 1

来自 MDN :

The bind() function creates a new function (a bound function) with the same function body (internal Call attribute in ECMAScript 5 terms) as the function it is being called on (the bound function's target function) with the this value bound to the first argument of bind(), which cannot be overridden.

基本上这意味着您不能在已绑定(bind)的函数上调用绑定(bind)。

在您的示例中，您必须执行以下操作:

func2 = someuser.func.bind(someuser);