逗号运算符何时有用？ [英] When is the comma operator useful?

问题描述

我在表达式中读到了这个关于逗号运算符的问题（，）和 MDN docs关于它，但我想不出它有用的场景。

I read this question about the "comma operator" in expressions (,) and the MDN docs about it, but I can't think of a scenario where it is useful.

那么，逗号运算符何时有用？

So, when is the comma operator useful?

推荐答案

下面的内容可能不是很有用，因为你不是自己编写的，但是minifier可以使用逗号运算符来缩小代码。例如：

The following is probably not very useful as you don't write it yourself, but a minifier can shrink code using the comma operator. For example:

if(x){foo();return bar()}else{return 1}

将成为：

return x?(foo(),bar()):1

？ ： 运算符现在可以使用，因为逗号运算符（在某种程度上）允许将两个语句写成一个语句。

The ? : operator can be used now, since the comma operator (to a certain extent) allows for two statements to be written as one statement.

这个是有用的，因为它允许一些整洁的压缩（这里是39 - > 24字节）。

This is useful in that it allows for some neat compression (39 -> 24 bytes here).

我想强调一下 var a，b 中的逗号是 不是 逗号运算符，因为它不存在于表达式中。逗号在 var 语句中具有特殊含义。表达式中的 a，b 将引用这两个变量并计算为 b ，但情况并非如此 var a，b 。

I'd like to stress the fact that the comma in var a, b is not the comma operator because it doesn't exist within an expression. The comma has a special meaning in var statements. a, b in an expression would be referring to the two variables and evaluate to b, which is not the case for var a, b.

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