本例檢測輸入變量的值。如果值是錯誤的,會拋出一個異常(錯誤)。catch 會捕捉到這個錯誤,並顯示一段自定義的錯誤消息:
<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 First JavaScript</h1>
<p>Please input a number between 5 and 10:</p>
<input id="demo" type="text">
<button type="button" οnclick="myFunction()">Test Input</button>
<p id="mess"></p>