??? ??????
??? ??? ???? ?? ??? ??? ? ????.
JavaScript ??
??? ??? ?? ?? ??? ???? ????? ?? ??? ???? ?? ?????.
JavaScript? ??? ??? ??? ?????.
for - ?? ???? ?? ??? ?????.
for/in - ??? ??? ?????.
while - ?? ?????. ??? ??? true???. ??? ?? ??
do/while - ??? ??? true? ?? ??? ?? ??? ?????.
For ??
for ??? ??? ?? ? ?? ?????. ?? ??? ????.
??? for ??? ?????.
for (? 1; ? 2; ? 3)
{
??? ?? ??
}
??? ? 1(?? ??)? ???? ?? ?????. .
Statement 2? ??(?? ??)? ???? ??? ?????.
Statement 3? ??(?? ??)? ??? ?? ?????.
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>點擊按鈕循環(huán)代碼5次。</p>
<button onclick="myFunction()">點擊這里</button>
<p id="demo"></p>
<script>
function myFunction(){
var x="";
for (var i=0;i<5;i++){
x=x + "該數(shù)字為 " + i + "<br>";
}
document.getElementById("demo").innerHTML=x;
}
</script>
</body>
</html>Run ??? ? ????
from ?? ??? ??? ? ? ????.
Statement 1? ??? ???? ?? ??(var i=0)? ?????.
Statement 2? ?? ?? ??? ?????(i? 5?? ??? ?).
Statement 3 ?? ??? ??? ??? ?(i++)? ??????.
Statement 1
????? ?? 1? ???? ??? ???? ??? ??????(var i=0).
? 1? ?? ????? ? 1? ???? ??? ??? ? ????.
? 1?? ???(?? ??) ?? ???? ? ????.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<script>
cars=["小明","小龍","小奇","小濤"];
for (var i=0,l=cars.length; i<l; i++){
document.write(cars[i] + "<br>");
}
</script>
</body>
</html>????? ???? ??? ???
? 1? ??? ?? ????(?: ??? ???? ?? ?? ??? ??). :
Example
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<script>
cars=["BMW","Volvo","Saab","Ford"];
var i=2,len=cars.length;
for (; i<len; i++){
document.write(cars[i] + "<br>");
}
</script>
</body>
</html>????? ???? ??? ???
Statement 2
?? 2?? ??? ?? ??? ??? ????? ?????.
?? 2? ???????.
? 2? true? ???? ??? ?? ????, false? ???? ??? ?????.
NOTE: ? 2? ???? ?? ?? ??? break? ???? ???. ??? ??? ???? ?? ? ????. ?? ?? ????? ??? ? ????.
? 3
?? ? 3? ?? ??? ?? ??????.
? 3? ???????.
? 3? ??? ??? ?????. ??? ??(i--)??? ? ? ? ????(i=i+15).
? 3? ??? ? ????(?: ?? ??? ?? ??? ?? ??):
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<script>
cars=["BMW","Volvo","Saab","Ford"];
var i=0,len=cars.length;
for (; i<len; ){
document.write(cars[i] + "<br>");
i++;
}
</script>
</body>
</html>????? ???? ??? ???
For/In ??
JavaScript for/in ? ???? ??? ??? ?????:
?
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>點擊下面的按鈕，循環(huán)遍歷對象 "person" 的屬性。</p>
<button onclick="myFunction()">點擊這里</button>
<p id="demo"></p>
<script>
function myFunction(){
var x;
var txt="";
var person={fname:"Bill",lname:"Gates",age:56};
for (x in person){
txt=txt + person[x];
}
document.getElementById("demo").innerHTML=txt;
}
</script>
</body>
</html>????? ???? ??? ???
???? while ??? do/while ??? ?? ???????. ?.
