1 onerror事件，实例代码如下：
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Demo2.aspx.cs" Inherits="WebApplication5.Demo2" %>
<script type="text/javascript">
function HandleError(sMessage,sURL,sLine) {
alert("出错了. "+"消息:"+sMessage+" URL:"+sURL+" 出错行号:"+sLine);
return true;
}
window.onerror = HandleError;
</script>
<body onload="HandleLoad()"></body>
2 try ... catch... finally ,实例代码如下：
<script type="text/javascript">
try
{
//alert("ok");
windows.open("about:blank");
}
catch (exception) {
alert("an error processed");
}
finally {
alert("finally");
}
alert("ok");
</script>
注意：与JAVA/C#语言不同的是，不支持多重catch语句，但支持嵌套catch语句
实例代码如下：
<script type="text/javascript">
try
{
var a = document.getElementById("txtUser");
alert(a.value);
}
catch (ex) {
try
{
alert(ex.message);
}
catch (ex) {
alert(ex.message);
}
}
</script>
错误类型判断
方法1.通过name属性判断；
方法2：通过instanceof操作符
实例代码如下：
<script type="text/javascript">
try
{
var scriptStr="var a=0;var b=1;var c=a++b;alert(c)";
eval(scriptStr);
}
catch (ex) {
if (ex instanceof SyntaxError) {
alert("语法出错了");
}
}
</script>
抛出异常
ECMAScript还引入throw语句，用于抛出异常，语法如下：
throw error_object,
error_object可以是字符串，数字，布尔值或是实际的对象，如
throw "an error occurred";
throw 5009
throw true;
throw new Object();
throw new Error();
throw new Error("error");
throw new Error(10001,"error");
自定义异常:实例代码如下：
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="js自定义异常.aspx.cs" Inherits="WebApplication5.js自定义异常" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<script type="text/javascript">
var EmailError = new Error(1001, "Email格式非法");
EmailError.name = "EmailFormatError";
EmailError.writeLog = function (funcname) {
var logstr = "error-code:" + this.number + " " + "error-message:" + this.message + " " + "error-type:" + this.name + " " + "error-func:" + funcname + " " + "error-time:" + (new Date()).toString();
alert(logstr);
}
function calc() {
var obj = document.getElementById("txtEmail");
try{
if(obj.value.indexOf("@")==-1)
{
throw EmailError;
}
else
{
alert("验证通过");
}
}
catch (ex) {
ex.writeLog("calc");
}
}
</script>
</head>
<body>
<form runat="server">
<div>
<input type="text" />
<input type="button" value="Calc" onclick="calc()" />
</div>
</form>
</body>
</html>