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Conditional statements in JavaScript are used to perform different actions based on different conditions.
假设语句在JS中用来依据不同的条件执行不同的行为。
Switch statement[开关语句]
How to write a switch statement.
怎样写switch(开关)语句
You should use the switch statement if you want to select one of many blocks of code to be executed.
如果想杂在几个代码块中选择一个来运行就使用switch(开关)语句
switch(n) { case 1: execute code block 1 break case 2: execute code block 2 break default: code to be executed if n is different from case 1 and 2 } |
This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically.
它是这样工作的:首先,有唯一的一个表达式 n (大多数为一个变量),它是被赋过值的。 接下来表达式将与每个case(事件)进行比较。如果吻合就执行该事件内的代码块。使用break来防止代码执行后自动转向下一个事件。
<script type="text/javascript"> //You will receive a different greeting based //on what day it is. Note that Sunday=0, //Monday=1, Tuesday=2, etc. var d=new Date() theDay=d.getDay() switch (theDay) { case 5: document.write("Finally Friday") break case 6: document.write("Super Saturday") break case 0: document.write("Sleepy Sunday") break default: document.write("I'm looking forward to this weekend!") } </script> |