一个检测表单数据的JavaScript实例，很简单，很实用，感兴趣的朋友可以看看

<div> 
  <label for="secondfield"&gt;Second Field:</label><br /> 
  <input id="secondfield" name = "secondfield" type = "text" /> 
</div> 

<div> 
  <label for="thirdfield"&gt;Third Field(numeric):</label><br /> 
  <input id="thirdfield" name = "thirdfield" type = "text" /> 
</div> 

<div> 
  <label for="fourthfield"&gt;Fourth Field:</label><br /> 
  <input id="fourthfield" name = "fourthfield" type = "text" /> 
</div> 

<input type="submit" value = "Send Data" />