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JavaScript 条件语句

2022-04-21

当条件满足时 （if……)

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if (条件) {
    // Code
}

例子：

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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
</head>
<body>
	<p id="data"></p>
<script>
var a, b, c;
a = 1; b = 2;
c = a+b;

if (c==3) {
	document.getElementById('data').innerHTML = c;
}
</script>
</body>
</html>

当条件满足和不满足时 (if……else)

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if (条件) {
	// 代码块
} else {
	// 代码块
}

例子：

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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
</head>
<body>
	<p id="data"></p>
<script>
var a, b, c;
a = 1; b = 2;
c = a+b;

if (c==3) {
	c = "满足"
} else {
	c = "不满足"
}
	document.getElementById('data').innerHTML = c;
</script>
</body>
</html>

多个条件执行 (if……else if……else )

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if (条件) {
    // 代码块
} else if (条件) {
	// 代码块
} else {
    // 代码块
}

例子：

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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
</head>
<body>
	<p id="data"></p>
<script>
var a, b, c;
a = 1; b = 3;
c = a+b;

if (c==3) {
	c = "满足"
} else if (c==4) {
	c = "还算满足"
} else {
	c = "不满足"
}
document.getElementById('data').innerHTML = c;
</script>
</body>
</html>
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