方法Set.prototype.add调用不兼容的接收器undefined

Question

我根本无法理解为什么它会给出这个错误.

这是我在chrome控制台上测试的内容:

>    var mySet;
<-   undefined

>    mySet = new Set;
<-   Set {}

>    mySet.add('foo', 'bar', 'baz')       // Worked as expected
<-   Set {"foo"}                          // just the first argument was added

>    ['bar', 'baz'].forEach(mySet.add)
X->  VM1529:1 Uncaught TypeError: 
         Method Set.prototype.add called on incompatible receiver undefined(…)

提前致谢.

Answer 1

在这种情况下,当您将其作为回调传递时,add方法会丢失其内部this上下文,因此您需要使用bind:

['bar', 'baz'].forEach(mySet.add.bind(mySet));