javascript 怎么判断 select

[liumin3285]

怎么用javascript 判断

      <select name="select">
        <option value="">请选择</option>
        <option value="A">A</option>
        <option value="B">B</option>
        <option value="C">C</option>
        <option value="D">D</option>
        <option value="E">E</option>
      </select>

document.form1.select.value==""这样接收不到值
假如为空就提示！！

[BeenZ]

你没有form1,当然没值

document. select .value

[hookee]

name="select" 属性值内不要有空格

<script>
function check(){
  if(document.form1.select.selectedIndex==0){
  	alert("请选择")
  	return false;
  }
}	
</script>

<form name="form1" id="form1">
<select name="select"> 
                <option  value= " "> 请选择 </option> 
                <option   value= "A "> A </option> 
                <option   value= "B "> B </option> 
                <option   value= "C "> C </option> 
                <option   value= "D "> D </option> 
                <option   value= "E "> E </option> 
            </select> 
<input type="button" value="click" onclick="check();">
</form>

[familyX]

<select   name= "select" id="select">
                <option   value= " "> 请选择 </option>
                <option   value= "A "> A </option>
                <option   value= "B "> B </option>
                <option   value= "C "> C </option>
                <option   value= "D "> D </option>
                <option   value= "E "> E </option>
            </select> 

alert(document.getElementById("select").options[document.getElementById("select").selectedIndex].value)