1.throw(拋出異常)，可與try/catch一起用
<html>
<body>
<script type="text/javascript">
var x=prompt("請輸入 0 至 10 之間的數：","")
try
{
if(x>10)
throw "Err1"
else if(x<0)
throw "Err2"
else if(isNaN(x))
throw "Err3"
}
catch(er)
{
if(er=="Err1")
alert("錯誤！該值太大！")
if(er == "Err2")
alert("錯誤！該值太小！")
if(er == "Err3")
alert("錯誤！該值不是數字！")
}
</script>
</body>
</html>
2.onerrer捕獲錯誤信息
<html>
<head>
<script type="text/javascript">
onerror=handleErr
var txt=""
function handleErr(msg,url,l)
{
txt="There was an error on this page.\n\n"
txt+="Error: " + msg + "\n"
txt+="URL: " + url + "\n"
txt+="Line: " + l + "\n\n"
txt+="Click OK to continue.\n\n"
alert(txt)
return true
}
function message()
{
adddlert("Welcome guest!")
}
</script>
</head>
<body>
<input type="button" value="View message" />
</body>
</html>