JS获取HTML元素标记名的三种常用方法

document.getElementById('demo') //demo是元素对应的ID

document.getElementsByTagname('li') //li是标签的名字

<p id="targetp" >2333333</p>
<script>
  var element = document.getElementById("targetp");
  var tagname = element.tagName;
  alert(tagname);
</script>

$("#content-header").get(0).tagName

<p onclick="alert('您单击的是：'+this.tagName);">中华人民共和国</p>

var demo = document.getElementById('demo');
var lis = demo.getElementsByTagname('li');   

document.getElementsByClassName('demo')  //demo为元素指定的class名

function getElementsByClassName(node,classname){
    if(node.getElementsByClassName) {
      return node.getElementsByClassName(classname);
    }else {
      var results = [];
      var elems = node.getElementsByTagName("*");
      for(var i = 0; i < elems.length; i++){
        if(elems[i].className.indexOf(classname) != -1){
          results[results.length] = elems[i];
        }
      }
      return results;
    }
  }