1、try语句测试代码错误
2、catch语句处理错误
3、throw语句创建自定义错误
4、例子：
语法：try
{
运行的代码
}
catch (err)
{
处理错误
}
eg：使用catch处理错误
<DOCUMENT html>
<html>
<head>
<script>
var txt="";
function message()
{
tey{
adddlert("hello");
}
catch(err)
{
txt="There was an error on this page.\n\n";
txt+="Error :"+err.message+"\n\n";
txt+="Click to continue.\n\n";
}
}
</script>
</head>
<bpdy>
<input type="button"value="View message"onclick="message()">
</body>
</html>
下面这个例子创建自定义错误并扑捉错误：
<script>
function myFunction()
{
try{
var x=document.getElementById("demo").value;
if(x=="") throw "empty";
if(isNaN(x)) throw "not a number";
if(x>10) throw "too high";
if(x<5) throw "too low";
}
catch(err)
{
var y=document.getElementById("mess");
y.innerHTML="Error:"+err+".";
}
}
</script>
<h1>My Function</h1>
<p>input between 5 and 10:</p>
<input id="demo" type="text">
<button type="button" onclick="myFunction()">test input</button>
<p id="mess"></p>