break语句用于提早退出循环,使之脱离封闭的花括号。break语句退出循环。
让我们看一个不使用label的JavaScript中的break语句示例-
<html>
<body>
<script>
var x = 1;
document.write("Entering the loop<br /> ");
while (x < 20) {
if (x == 5){
break; // breaks out of loop completely
}
x = x + 1;
document.write( x + "<br />");
}
document.write("Exiting the loop!<br /> ");
</script>
</body>
</html>标签用于控制程序的流程,也就是说,在嵌套的for循环中使用它来跳转到内部或外部循环。您可以尝试使用break语句运行以下代码以使用标签来控制流程-
<html>
<body>
<script>
document.write("Entering the loop!<br /> ");
outerloop: // This is the label name
for (var i = 0; i < 5; i++) {
document.write("Outerloop: " + i + "<br />");
innerloop:
for (var j = 0; j < 5; j++) {
if (j > 3 ) break ; // Quit the innermost loop
if (i == 2) break innerloop; // Do the same thing
if (i == 4) break outerloop; // Quit the outer loop
document.write("Innerloop: " + j + " <br />");
}
}
document.write("Exiting the loop!<br /> ");
</script>
</body>
</html>