JavaScript中的x ++有什么作用? [英] What does x++ in JavaScript do?

问题描述

我有一个很短的问题，但这确实使我感到困惑.

I have a very short question, but it really confused me.

var y = 3, x = y++;

x的值是什么?

我认为答案应该是4，但实际上是3.

I thought the answer should be 4, but actually it's 3.

有人可以向我解释原因吗?

Can anyone explain me the reason?

推荐答案

y ++ 被称为 post-increment (后递增)-在变量之后它会递增变量>它返回原始值作为表达式的值.所以

y++ is called post-increment -- it increments the variable after it returns the original value as the value of the expression. So

x = y++;

等效于:

temp = y;
y = y + 1;
x = temp;

如果要返回新值，则应使用 ++ y .之所以称为 pre-increment ，是因为它会在返回变量 之前将其递增.声明

If you want to return the new value, you should use ++y. This is called pre-increment because it increments the variable before returning it. The statement

x = ++y;

等效于:

y = y + 1;
x = y;

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