表单正则表达式

<script>

function strIsNull(str)  
{  
var patrn=/[a|b|c]/; 
if (!patrn.exec(str)) return false
return true
}
 
function cheack(form){
if(strIsNull(form.name.value))
{
alert("aaaaaaaaaaaa");
return false;
}
else
{
alert("111111111111");
return true;
}
}
</script>
<form id="form" name="form" method="post" action="" onsubmit="return cheack(this);">
  <input type="text" name="name" />
  <input type="submit" name="Submit" value="提交" />
</form>