TypeError：getElementById为null [英] TypeError: getElementById is null
问题描述
<html>
<head>
<script type="text/javascript">
var image = document.getElementById(image);
var desc = document.getElementById(desc);
var images = ["http://i.imgur.com/XAgFPiD.jpg", "http://i.imgur.com/XAgFPiD.jpg"]
var descs = ["1", "2"]
var num = 0;
var total = images.length;
function clicked(){
num = num + 1;
if (num > total){
num = 0;
}
image.src = images[num];
desc.innerHTML = images[num];
}
document.getElementById(submit).onclick(clicked());
</script>
</head>
<body>
<div><h2>Project |</h2><h2> | herbykit</h2></div>
<div>
<button id="submit">Next</button><br/>
<img id="image" src="http://i.imgur.com/XAgFPiD.jpg" height="20%" width="50%"/>
<p id="desc">first desc.</p>
</div>
</body>
</html>
document.getElementById（submit）.onclick（clicked（））;行抛出错误
ReferenceError：未定义提交
The line "document.getElementById(submit).onclick(clicked());" throws an error "ReferenceError: submit is not defined"
当我尝试访问常规按钮时
[通过getElementsByClassName& getElementsByTagName]
，它给出了错误 ReferenceError：未定义按钮。
When I tried accessing buttons in general
[through getElementsByClassName & getElementsByTagName]
it gave an error of "ReferenceError: button is not defined"
在getElementById中使用字符串会引发错误 getElementById为null
Using strings in getElementById it throws the error "getElementById is null"
我发现了几个问题和答案。
I found several questions and answers to this.
我只有一个人知道如何实现，由于使用了PHP，而这在大多数其他情况下都是错误。我发现的其他解决方案在数字上涉及错误。
针对此错误，我尝试修复了printwindow.document.getElementById（.. etc
。这给了我一个错误 ReferenceError：未定义printwindow。
Only one of them I understood how to implement, due to the use of PHP and that being the error on most others. Other solutions I found involved errors numerically. On this error I tried a fix of printwindow.document.getElementById(..etc This gives me an error of "ReferenceError: printwindow is not defined"
推荐答案
浏览器会尽快运行JavaScript以加快渲染速度，因此当您收到以下代码时：
Browsers run JavaScript as soon as possible in order to speed up rendering. So when you receive this code:
<html>
<head>
<script type="text/javascript">
var image = document.getElementById(image); // Missing quotes, typo?
...在中间运行。没有< foo id = image> 在页面上，所以您得到 null 。最后，您将获得页面的其余部分呈现的内容，包括：
... in runs intermediately. There's no <foo id="image"> on page yet, so you get null. Finally, you get the rest of the page rendered, including:
<img id="image" src="http://i.imgur.com/XAgFPiD.jpg" height="20%" width="50%"/>
为时已晚
您需要绑定一个window.onload甚至处理程序并运行您的代码DOM准备就绪时（或将所有JavaScript移到图片底部的页面底部）编写代码。
You need to bind a window.onload even handler and run your code when the DOM is ready (or move all JavaScript to page bottom, after the picture).
这篇关于TypeError：getElementById为null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
