javascript var charCode = (evt.which) ? evt.which : event.keyCode;
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javascript var charCode = (evt.which) ? evt.which : event.keyCode;
提问by Painkiller
how a code var charCode = (evt.which) ? evt.which : event.keyCodecould be explaned?
what happens here ?
all i understand is that clause returns buttons value to the object charCode.
but what those ? and : signs mean?
and can i use this thing in other languager? java/c++/php and so on?
Thanks
如何解释代码var charCode = (evt.which) ? evt.which : event.keyCode？这里会发生什么？我所理解的是该子句将按钮值返回给对象 charCode。但那些是什么？和：标志是什么意思？我可以在其他语言中使用这个东西吗？java/c++/php 等等？谢谢
回答by James Allardice
It's called the ternary conditional operator. It's basically short for an if...else:
它被称为三元条件运算符。它基本上是 an 的缩写if...else：
var charCode;
if(evt.which) {
charCode = evt.which;
}
else {
charCode = evt.keyCode;
}
Basically, it evaluates the first operand. If that evaluation returns true, the second operand is returned. If false, the third is returned.
基本上，它评估第一个操作数。如果该评估返回true，则返回第二个操作数。如果false，则返回第三个。
As for whether you can use it in other languages, you often can. From the languages you listed, Java and PHP both have it, and I'd be very surprised if C++ didn't (edit - a quick Google reveals that C and C++ do indeed support it too). For more, see Wikipedia.
至于是否可以在其他语言中使用它，您经常可以。从你列出的语言来看，Java 和 PHP 都有，如果 C++ 没有，我会非常惊讶（编辑 - 一个快速的谷歌显示 C 和 C++ 确实也支持它）。有关更多信息，请参阅维基百科。
回答by Konrad Borowski
First, of all, var charCode =starts assignment to local charCodevariable. Next, ternary operatoris used. It compounds of three parts, condition, what happens if it's true and what happens if it's false.
首先，var charCode =开始对局部charCode变量赋值。接下来，使用三元运算符。它由三部分组成，条件，如果是真的会发生什么，如果是假的会发生什么。
(evt.which) ? evt.which : event.keyCode
# condition # if true # if false
In this case, it's used for feature detection (keyboard key event). evt.whichis proper way to do it, but in very old browsers you may want to use event.keyCode.
在这种情况下，它用于特征检测（键盘按键事件）。evt.which是正确的方法，但在非常旧的浏览器中，您可能想要使用event.keyCode.
回答by rob
Others correctly pointed out that it is shorthand for:
其他人正确地指出它是以下的简写：
var charCode;
if(evt.which) {
charCode = evt.which;
}
else {
charCode = evt.keyCode;
}
but it is also longhand for:
但它也适用于：
var charCode = evt.which || evt.keyCode;
回答by Ash Burlaczenko
This is called the conditional operator.
这称为条件运算符。
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Operators/Conditional_Operator
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Operators/Conditional_Operator
To the left of the ?is the condition. To the right are to results seperated by a :. If the condition is true, the result on the left of the colon is used, otherwise the it's the result on the right.
的左边?是条件。右边是由 a 分隔的结果:。如果条件为真，则使用冒号左侧的结果，否则使用冒号右侧的结果。
