无法获取属性'addEventListener' [英] Unable to get property 'addEventListener'
问题描述
我今天一直在研究我的应用程序的一个小方面，并希望在我的应用程序上获得一个滑动条。今天早上我问了一个问题，那里有一些很好的答案。我最近想试着回答我给出的脚本， CSS 和 HTML 。
I have been working on a small aspect of my application today and wanted to get a sliding bar on my application. I asked a question this morning where there was some good answers. I have recently wanted to try and answer that i ws given using Script, CSS and HTML.
我得到脚本时遇到问题，因为它一直在提示错误：
I am getting to problem to get the Script working as it keeps coming up with an error saying:
0x800a138f - JavaScript runtime error: Unable to get property 'addEventListener' of undefined or null reference
这是脚本：
This is the Script:
<script type="text/javascript">
var desktops = document.querySelectorAll('.desktop');
function hide(element) {
element.style.setProperty('left', '-100%', element.style.getPropertyPriority('left'));
}
function hideAll() {
for (var i = 0; i < desktops.length; i++) {
hide(desktops[i]);
}
}
function show(element) {
element.style.setProperty('left', '0', element.style.getPropertyPriority('left'));
}
document.getElementById('link-one').addEventListener('click', function () {
hideAll();
show(document.getElementById('one'));
}, false);
show(document.getElementById('one'));
</script>
以下是 HTML ：
Here is the HTML:
<ul>
<li id="link-one">
<div>1</div>
<div>One</div>
</li>
</ul>
<div id="one" class="desktop">
<h1>Sidebar Example</h1>
<p>This is 1</p>
<p>Something here.</p>
</div>
从我能解决的问题看，它无法找到ID？
From what I can work out its not being able to find the ID?
推荐答案
问题在于，在创建页面上的元素之前，您正在运行脚本。这就是为什么 getElementById 返回 null 。
The problem is that you're running the script BEFORE the elements on the page have been created. That is why the getElementById is returning null.
有几种方法可以解决这个问题......
There are several ways to get around this...
- （如Kendall所述），您可以将脚本移动到
< body> - 您可以将代码放入函数中，并从
< body onload =newFunction（）;> - 如果您可以使用jQuery，可以将代码包装在
）{...}）;
- (as commented by Kendall) you can move the script to the end of the
<body> - You can put your code in a function, and call that function from
<body onload="newFunction();"> - If you can use jQuery, you can wrap the code in
$(function() { ... });
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