javascript 为什么我收到 TypeError: obj.addEventListener is not a function？
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why am I getting TypeError: obj.addEventListener is not a function?
提问by max7
Here's my code:
这是我的代码：
function addEvent( obj, type, fn ) {
if ( obj.attachEvent ) {
obj['e'+type+fn] = fn;
obj[type+fn] = function(){obj['e'+type+fn]( window.event );}
obj.attachEvent( 'on'+type, obj[type+fn] );
} else
obj.addEventListener(type, fn, false);
}
function alertWinner(){
alert("You may be a winner!");
}
function showWinner (){
var aTag = document.getElementsByTagName("a");
addEvent(aTag, 'click', alertWinner);
}
showWinner();
Basically, I'm working in the firebug console and trying to get an alert to pop up when any a tag is clicked.
基本上，我在 firebug 控制台中工作，并试图在单击任何标签时弹出警报。
I can't see the problem that results in this not working and giving me the error stated in my questions title (viewed in firebug). Anybody?
我看不到导致这不起作用的问题，并给我问题标题中所述的错误（在萤火虫中查看）。有人吗？
回答by Matt Zeunert
document.getElementsByTagNamereturns a NodeListof DOM elements. Each element has an addEventListenerfunction, but the array doesn't have one.
document.getElementsByTagName返回一个DOM 元素的NodeList。每个元素都有一个addEventListener函数，但数组没有一个。
Loop over it:
循环它：
function showWinner (){
var aTags = document.getElementsByTagName("a");
for (var i=0;i<aTags.length;i++){
addEvent(aTags[i], 'click', alertWinner);
}
}
回答by Sebas
aTagis an instance of DOMNodeList, not from DOMElement.
aTag是 的一个实例DOMNodeList，而不是来自DOMElement。
You could do this instead:
你可以这样做：
var aTags = document.getElementsByTagName("a");
var aTag = aTags[0];
But obviously this approach presents a flaw, in that there might be more than one aelement returned. You should use a different selector that returns only one element, if possible.
但显然这种方法存在一个缺陷，即可能a返回多个元素。如果可能，您应该使用仅返回一个元素的不同选择器。
回答by Jason Lydon
Not sure why, but I got addEvent is not definedin Firefox. I couldn't even find addEvent()on MDN. I had to use this:
不知道为什么，但我进入addEvent is not defined了 Firefox。我什至addEvent()在 MDN 上都找不到。我不得不使用这个：
function showWinner (){
var aTags = document.getElementsByTagName("a");
for (var i=0;i<aTags.length;i++){
// addEvent(aTags[i], 'click', alertWinner);
aTags[i].addEventListener("click", alertWinner);
}
}
