The problem is this
var id=document.getElementById(ele);
var cls=document.getElementsByClassName(ele);
var tag=document.getElementsByTagName(ele)Now we need to determine what type of ele it is and write it like this, that is,
For example, if I enter a label 'a', it means the label, #a means id, and .a means class to perform the corresponding operation
<body>
<p id="app">
测试1
</p>
<p>测试2</p>
<span class="span">测试3</span>
<script>
window.onload=function () {
function getreg(ele) {
var id=document.getElementById(ele);
var cls=document.getElementsByClassName(ele);
var tag=document.getElementsByTagName(ele)
alert(cls.getAttributeNode('p'))
}
getreg('app')
}
</script>
</body>The code is like this
Because there may be at least one element in the page
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
If you simply want to get the element, you can use
You must use the original idea to determine the input type