1.使用return關鍵字傳回函數執行後的結果
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script type="text/javascript">
function calcSum(num1, num2) {
var sum = num1 + num2;
return sum; //使用return關鍵字傳回函數執行後的結果
}
var sum = calcSum(2, 7);
console.log(sum * 2);
console.log(sum / 2);
</script>
</head>
<body>
</body>
</html>
2.如果return後面沒有跟傳回值或沒有使用return關鍵字，則預設傳回：undefined
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script type="text/javascript">
function calc1(num1, num2) {
console.log(num1 - num2);
return;
}
var result = calc1(7, 2);
console.log(result);
function calc2(num1, num2) {
console.log(num1 - num2);
}
var result2 = calc2(7, 2);
console.log(result2);
var result3 = alert("hhhhh");
console.log(result3);
</script>
</head>
<body>
</body>
</html>
3.return關鍵字作用：
1.傳回函數執行的結果
2.結束函數的執行
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script type="text/javascript">
function calc5(num1, num2) {
var sum = num1 + num2;
if (sum > 20) {
return; //結束函數的執行
}
console.log(sum);
}
calc5(3, 27)
</script>
</head>
<body>
</body>
</html>