是url返回true
不是返回false
<html><head>
<title>检查是否为URL</title>
<script language="javascript">
function check(){
str = form1.txt.value
str = str.match(/http:\/\/.+/)
if (str == null){
alert('你输入的URL无效')
return false
}else{
return true
}
}
</script>
</head>
<body>
<form name="form1" onSubmit="return check()">
<input type="text" name="txt">
<input type="submit" value="检验">
</form>
</body>
</html>
