js中获取表单/dom对象的方法

<form>
            <input  type="text"  value="请输入用户名" id=”number”><br />
            <input type=" button"   value="提交"  οnclick="checkForm()">
    </form>
JS部分

<script>
        funciton checkForm(){
        var obj=document.getElementById("number").value;
        alert(obj)
       }
</script>

<form id ="form1"  name=”form1”>
        代号:<input type="text" name="a" value="1"><br>
        代号:<input type="text" name="a" value="2"><br>
        代号:<input type="text" name="a" value="3"><br>
        <input  type="submit" value="提交">
   </form>  
 </body>
  <script  type="text/javascript">
         document.getElementById('form1').onsubmit=function(){   // div.οnclick=function(){}
         var as=document.getElementsByName('a');  //数组
        for(i=0; i<as.length;i++){
          alert(as[i].value);
         }
       }
    </script>

<script>
        funciton checkForm(){
             var obj=document.form1.number.value;
             var obj=document.forms[0].number.value;//
             var obj=document.forms[0]['number'].value;
             var obj=document.form1['number'].value;
       }
</script>