我從一本書中看到了這個例子,但是我沒有得到和本書相同的結果。沒有得到預期的結果 - javascript
兩個HTML頁面。
calcfactorialtopframe.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<script type="text/javascript">
function calcFactorial(factorialNumber) {
var factorialResult = 1;
for (; factorialNumber > 0; factorialNumber--) {
factorialResult = factorialResult * factorialNumber;
}
return factorialResult;
}
</script>
</head>
<body>
<frameset cols="100%,*">
<frame name="fraCalcFactorial" src="calcfactorial.html"></frame>
</frameset>
</body>
</html>
calcfactorial.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<script type="text/javascript">
function butCalculate_onclick() {
try {
if (window.top.calcFactorial == null) {
throw "This page is not loaded within the correct frameset";
};
if (document.form1.txtNum1.value == "") {
throw "!Please enter a value before you calculate its factorial";
};
if (isNaN(document.form1.txtNum1.value)) {
throw "!Please enter a valid number";
};
if (document.form1.txtNum1.value < 0) {
throw "!Please enter a positive number";
};
document.form1.txtResult.value = window.parent.calcFactorial(document.form1.txtNum1.value);
}
catch (exception) {
if (typeof(exception) == "string") {
if (exception.charAt(0) == "!") {
alert(exception.substr(1));
document.form1.txtNum1.focus();
document.form1.txtNum1.select();
} else {
alert(exception);
}
} else {
alert("The following error occurred " + exception.message);
}
}
}
</script>
</head>
<body>
<form action="" name="form1">
<input type="text" name="txtNum1" size="3" /> factorial is
<input type="text" name="txtResult" size="25" /><br />
<input type="button" value="Calculate Factorial" name="butCalculate" onclick="butCalculate_onclick()" />
</form>
</body>
</html>
我不斷收到錯誤 「此頁不正確的框架中加載」。
本書中練習的目的是爲了展示try catch拋出的工作原理。
感謝
這是一個相當複雜的方式來解釋'try ... catch'是如何工作的!你得到這個結果的原因是因爲'window.top.calcFactorial' _is_'null',所以'try'語句中的'throw'n異常,將它輸出(或_referring_)到'catch'。我其實不認爲iFrames可以訪問他們父母的javascript函數,所以它顯然是'null'。對於'try ... catch'的一個很好的解釋,查看MDN:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/try.catch – somethinghere 2014-12-01 16:53:45
你的try catch正在'if(window.top.calcFactorial == null)'是throwig錯誤 – ConfusedShark 2014-12-01 16:54:45
我將閱讀提供的鏈接。謝謝你的幫助。 – 2014-12-01 17:07:39