javascript 使用 addEventListener 与旧式属性的 readystatechange？
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readystatechange using addEventListener versus old-style property?
提问by Delan Azabani
readystatechangeis a standard event for XMLHttpRequestobjects, and so should be able to have functions listen on the event either using
readystatechange是XMLHttpRequest对象的标准事件，因此应该能够让函数使用
r.onreadystatechange = function() { ... };
as well as
也
r.addEventListener('readystatechange', function() { ... }, false);
However, the latter method only seems to work in Firefox and Chrome, but not Opera, which does not throw an error but simply has no effect. Why is this, and is this even correct behaviour?
然而，后一种方法似乎只适用于 Firefox 和 Chrome，但不适用于 Opera，它不会抛出错误，但根本没有效果。为什么会这样，这甚至是正确的行为吗？
采纳答案by dtech
The MDN docs on XMLHttpRequestdon't specifically mention raising a readystatechangeevent, but the W3C docsdo require it.
XMLHttpRequest 上的MDN 文档没有特别提到引发readystatechange事件，但W3C 文档确实需要它。
That combined with the general rule "onxxxis the event handler for event xxx" would imply that the Opera behaviour is incorrect.
结合一般规则“onxxx是事件的事件处理程序xxx”将意味着 Opera 行为是不正确的。
回答by jantje19
This worked for me.
这对我有用。
xhr.addEventListener('readystatechange', evt => {
if (this.readyState == 4 && this.status == 200) {
console.log(this.responseText);
return this.responseText;
}
}, false);
