无法将属性InnerHTML设置为null [英] Cannot set property InnerHTML of null
问题描述
我有一个简单的html页面，body标签中没有代码。
我想通过javascript在body标签中插入html。
I've a simple html page with no code in the body tag. I want to insert the html in the body tag through javascript.
我的javascript文件看起来像这样。
My javascript file looks like this.
var Global={
UserWall:function(){
return "a very long html code";
}
};
var globalObject=Object.create(Global);
document.getElementsByTagName("body").item(0).innerHTML=globalObject.UserWall();
现在我希望在页面加载时将这个非常长的html代码自动插入到body标签中。
但它给了我在标题中提到的错误。为什么？
Now I want this very long html code to be auto inserted in the body tag on page load. But it is giving me the error I've mentioned in the title.Why?
这也是创建基于ajax的网站的正确方法（不页面重新加载）意味着如果我调用服务器端脚本来更新这个非常长的html代码并将其附加到页面正文。
and also is this the correct way to create ajax based website(no page reloads) meaning that if I called server side script to update this very long html code and appended it to the body of the page.
推荐答案
在构建DOM之前，您几乎肯定会运行代码。尝试在 window.onload 中运行代码处理函数（但请参阅下面的注释）：
You are almost certainly running your code before the DOM is constructed. Try running your code in a window.onload handler function (but see note below):
window.onload = function() {
// all of your code goes in here
// it runs after the DOM is built
}
另一种流行的跨浏览器解决方案是在结束< / body> < script> 块>标签。根据您的需要，这可能是最佳解决方案：
Another popular cross-browser solution is to put your <script> block just before the closing </body> tag. This could be the best solution for you, depending on your needs:
<html>
<body>
<!-- all of your HTML goes here... -->
<script>
// code in this final script element can use all of the DOM
</script>
</body>
</html>
- 请注意
window.onload将等到所有图像和子帧都已加载，这可能需要很长时间才能构建DOM。您还可以使用document.addEventListener（DOMContentLoaded，function（）{...}）来避免此问题，但跨浏览器不支持此功能。底部技巧是跨浏览器并在DOM完成后立即运行。 - Note that
window.onloadwill wait until all images and subframes have loaded, which might be a long time after the DOM is built. You could also usedocument.addEventListener("DOMContentLoaded", function(){...})to avoid this problem, but this is not supported cross-browser. The bottom-of-body trick is both cross-browser and runs as soon as the DOM is complete.
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