JavaScript ?? ????
JavaScript ??? ???? ?? ???? ????.
?? ??? ????(Parameters) ? ??? ????(Arguments)
?? ?????? ??? ??? ????? ?? ?????.
????????????????????? // ??? ??...}??? ?? ????? ?? ?? ? ??? ???? ?? ????.
?? ?? ? ???? ?? ????? ?????.
???? ??
JavaScript ?? ??? ????? ??? ??? ???? ??? ?????.
?? ????
??? ??? ????? ???? ?? ???? ????? ????? ??? ?? ?????. ????? ???? ?? ???? ???:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>設(shè)置參數(shù)的默認(rèn)值。</p>
<p id="demo"></p>
<script>
function myFunction(x, y) {
if (y === undefined) {
y = 0;
}
return x * y;
}
document.getElementById("demo").innerHTML = myFunction(4);
</script>
</body>
</html>????? ???? ??? ????? ? ??? ??:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>設(shè)置函數(shù)參數(shù)默認(rèn)值。</p>
<p id="demo"></p>
<script>
function myFunction(x, y) {
y = y || 0;
return x * y;
}
document.getElementById("demo").innerHTML = myFunction(4);
</script>
</body>
</html>????? ???? ??? ???
Tip
: y? ??? ?? y | |? y? true?? ??? y? ????, ??? ??? ???? ??? false??? 0? ?????.?? ?? ? ????? ?? ?? ???? ?? ???? ??? ?? ? ?? ?? ????? ???? ????. ?? ??? ???? ??? ? ????.
Arguments ??JavaScript ???? ?? ?? ?? ??? ????.
argument ???? ?? ??? ???? ??? ???? ????.
? ???? ??? ????? ?? ?? ?? ? ????:<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>查找最大的數(shù)。</p>
<p id="demo"></p>
<script>
function findMax() {
var i, max = 0;
for(i = 0; i < arguments.length; i++) {
if (arguments[i] > max) {
max = arguments[i];
}
}
return max;
}
document.getElementById("demo").innerHTML = findMax(4, 5, 6);
</script>
</body>
</html>????? ???? ??? ????? ?? ?? ?? ???? ??? ?????: <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>計(jì)算所有參數(shù)之和：</p>
<p id="demo"></p>
<script>
function sumAll() {
var i, sum = 0;
for(i = 0; i < arguments.length; i++) {
sum += arguments[i];
}
return sum;
}
document.getElementById("demo").innerHTML =
sumAll(1, 123, 500, 115, 44, 88);
</script>
</body>
</html>????? ???? ??? ??? ??? ???? ??
???? ???? ????? ??? ??? ???????. JavaScript ??? ????? ??? ?????. ??? ?? ?????.
??? ???? ?? ???? ?? ??? ????(?? ???? ???)? ?? ?? ???? ????. ??? ????? ?? ??? ?? ??? ???? ????. ??? ?? ???? ??
JavaScript??? ??? ?? ??? ? ????.
??? ?? ???? ??? ??? ???? ??? ???? ?????.
?? ?? ??? ??(?? ??) ???? ??? ? ????.
??? ?? ??? ?? ???? ? ? ????.
