你怎么看这个JavaScript代码？ （var1？var2：var3） [英] How do you read this JavaScript code? (var1 ? var2:var3)

问题描述

我在 JavaScript 代码中看到过这种格式，但找不到编辑后续内容：

感谢所有快速解答！我觉得它就像那样。现在，对于奖励积分：

你能用
（var1？var2）

来做同样的事情

  if（var1）{
 var2 
} 
  

？

解决方案

众所周知作为 三元 （因为它有三个操作数）条件（因为它是if / else / then）运算符。

它被计算为一个值，所以你通常会用它来分配一个值，例如：

  var result = condition？ value1：value2; 
  

相当于：

  var result; 
 if（condition == true）{
 result = value1; 
} else {
 result = value2; 
} 
  

例如：

  var message =长度是+ len ++（len == 1？foot：feet）; 
  

注意？：是完整的运营商。它不是？和：运算符，所以？ by在Javascript中本身毫无意义。

I've seen this format used in JavaScript code, but can't find a good source for the meaning.

Edit for a follow-up:

Thanks for all the quick answers! I figured it was something like that. Now, for bonus points:

can you use (var1 ? var2)

to do the same thing as

    if (var1) {
        var2
    }

?

解决方案

It's known as a ternary (because it has three operands) conditional (because it's an if/else/then) operator.

It is evaluated to a value, so you would usually use it to assign a value, such as:

var result = condition ? value1 : value2;

Which is equivalent to:

var result;
if (condition == true) {
  result = value1;
} else {
  result = value2;
}

An example:

var message = "Length is " + len + " " + (len==1 ? "foot" : "feet");

Note ?: is the full operator. It's not a ? and : operator, so ? by itself is meaningless in Javascript.

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