javascript - polymer 1.x : Event listener scope of "this" object

Question

我已经为我的 <iron-ajax> 添加了一个事件监听器到我的自定义元素中打电话。

问题

How to I reference the last-response property of the <iron-ajax> element from an imperatively defined event listener?

请参阅下面代码中的注释。

自定义元素.html

<template>
  ...
  <iron-ajax id="ajax" last-response="{{ajax}}"></iron-ajax>
  ...
<template>
<script>
  ...
  var t = this.$.ajax;
  t.addEventListener('response', function(e) {
    console.log(this.ajax); // undefined
    console.log(e); // Successfully logs response event object to console
  });
  ...
</script>

Answer 1

使用 Javascript bind() 改变函数中 this 的上下文:

var t = this.$.ajax;
t.addEventListener('response', function(e) {
  console.log(this); // this now = t
  console.log(e); // Successfully logs response event object to console
}).bind(t);

参见 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind