JavaScript DOM基础操作详解：节点、获取元素与属性管理

<h1>What do you want to buy</h1>
  <p title="a gentle reminder">Donnot Forget TO Buy This Stuff</p>
  <ul id="purchases">
    <li>A tin of beans</li>
    <li class="sale">Cheese</li>
    <li class="sale important">Milk</li>
  </ul>

var obj=document.getElementById("purchases");

var obj=document.getElementsByTagName('li')
alert(typeof obj);
alert(obj.length);
for(var i=0;i<obj.length;i++){
  alert(typeof obj[i]);
}

var obj=document.getElementsByClassName('sale');
alert("具有sale类的元素个数："+obj.length);
//important sale顺序颠倒不影响 ----getElementsByClassName('sale important')
var obj_1=document.getElementsByClassName(' important sale');
alert("同时具有important 和sale类的元素个数："+obj_1.length);

var pa=document.getElementsByTagName('p');
for(var i=0;i<pa.length;i++){
  var text=pa[i].getAttribute('title');
  if(text) alert(text);
}

var shoppping=document.getElementById('purchases');
shoppping.setAttribute('title','A list of goods');
alert(shoppping.getAttribute('title'));