JavaScript If...Else ?
???
????? ??? ??? ? ??? ??? ?? ?? ??? ??? ???? ???. ???? ???? ???? ? ??? ??? ? ????.
JavaScript??? ??? ?? ???? ??? ? ????.
if ? - ??? ??? true? ?? ??? ????? ? ?? ?????.
if...else ? - ??? true? ? ??? ????, ??? ? ?????. ??? false? ? ?? ??
if...else if....else ? - ??? ?? ?? ?? ? ??? ????? ? ?? ?????.
switch ? - ?? ?? ?? ? ??? ????? ? ?? ?????. ,
if ?? ?????.
??:
if (expr){
?
}
? ??? expr ?? true? ?? {statement}? ??? ?????.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
<script type="text/javascript">
var x = 3;
var y = 1;
if (x>y)
alert("x 大于 y");
</script>
</head>
<body>
</body>
</html>if…else
??:
if (expr) {
statement1
} else {
statement2
}
??? expr ????, ???1? ?????. ??? ??? ???2? ??????.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
<script type="text/javascript">
var x = 1;
var y = 3;
if (x>y){
alert("x大于y");
} else {
alert("x小于等于y");
}
</script>
</head>
<body>
</body>
</html>if...else if...else
??:
if (expr1){
?statement1
} else if (expr2) {
} else {
statement3
}
? ??? expr1? true? ???? statement1? ????, ??? ??? expr2? true? ?? expr2? ????, expr2? true? ???? statement3? ???? ?????.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
<script type="text/javascript">
var x = 3;
var y = 3;
if (x>y) {
alert("x大于y");
} else if (x<y) {
alert("x小于y");
} else {
alert("x等于y");
}
</script>
</head>
<body>
</body>
</html>
