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JavaScript ?? - throw, try and catch
try ?? ?? ??? ??? ??? ??????.
catch ? ?? ?????.
?? ?? ??? ?? ??? ?????.
JavaScript ??
JavaScript ??? JavaScript ??? ??? ? ??? ??? ??? ? ????.
?? ??? ? ????. ????? ?????? ?? ?? ??? ?????.
?? ????? ?? ??? ????? ? ????(???? ??? ??).
??? ???? ??? ???? ?? ??? ??? ? ????.
??, ??? ? ?? ?? ?? ???? ?? ??? ?? ????.
JavaScript?? ?? ??
??? ????? ??? ???? ????? JavaScript ??? ???? ?? ???? ?????.
? ??? ???? ?? ??? ??? ????. JavaScript?? ??? ?????. JavaScript try ? catch ?? ???? ?? ? ??? ????? ?? ??? ??? ? ????.
catch ?? ???? try ?? ???? ??? ??? ? ??? ?? ??? ??? ? ????.
JavaScript ?
try ? catch ? ??? ?????.
Syntax
try { //??? ?? ??
} catch(err) {//??? ?? ??}
Instances
?? ???? ?? try ??? ??? ????? ??? ????. Alert? ????? addlert
? ???????. catch ??? try ???? ??? ???? ??? ???? ?? ?????.<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>php中文網(wǎng)(php.cn)</title> <script> var txt=""; function message(){ try { adddlert("Welcome guest!"); } catch(err) { txt="本頁有一個錯誤。\n\n"; txt+="錯誤描述：" + err.message + "\n\n"; txt+="點擊確定繼續(xù)。\n\n"; alert(txt); } } </script> </head> <body> <input type="button" value="查看消息" onclick="message()" /> </body> </html>
????? ???? ??? ???
Throw ?throw ?? ???? ??? ?? ??? ?? ? ????.
??? ?? ??? ?? ?? ?? ?????.
try ? catch? ?? throw? ???? ???? ??? ???? ??? ?? ?? ???? ??? ? ????.
Syntax
throw ??
??? JavaScript ???, ??, ??? ?? ??? ? ????.
Example
? ??? ?? ??? ?? ?????. ?? ??? ??(??)? ?????. catch? ? ??? ???? ??? ?? ?? ???? ?????.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
<script>
function myFunction(){
try{
var x=document.getElementById("demo").value;
if(x=="") throw "值為空";
if(isNaN(x)) throw "不是數(shù)字";
if(x>10) throw "太大";
if(x<5) throw "太小";
}
catch(err){
var y=document.getElementById("mess");
y.innerHTML="錯誤：" + err + "。";
}
}
</script>
</head>
<body>
<h1>我的第一個 JavaScript</h1>
<p>請輸出一個 5 到 10 之間的數(shù)字:</p>
<input id="demo" type="text">
<button type="button" onclick="myFunction()">測試輸入</button>
<p id="mess"></p>
</body>
</html>????? ???? ??? ???
?? getElementById ??? ???? ?? ?? ???? ??? ?????.
