<!DOCTYPE><html><head> <meta http-equiv="Content-type" content="text/html" charset="utf-8"> <title>check file</title></head><body><b>文件扩展名验证</b><input type="text" name="int" value="文件.php" onblur="check(this)" id="int"><input type="button" value="检测" onclick="check_value()"><script> function check(obj){ if(obj.value == "" || obj.value.length<3){ alert("输入的长度不能小于3且不能为空!"); obj.focus(); } } function check_value(){ var str = $("int").value; var repx = /.(php|asp|jsp)$/i; var type = str.substring(str.lastIndexOf("."),str.length); if(type.match(repx) && str.lastIndexOf(".") != -1){ alert("文件扩展名正确"); $("int").focus(); }else{ alert("文件扩展名有误"); $("int").focus(); } } function $(obj){ return document.getElementById(obj); }</script></body></html>