JavaScript中的后缀和前缀增量 [英] Postfix and prefix increments in JavaScript

问题描述

我只是好奇一件事。 Javascript中的一个小例子

I'm just curious about one thing. A little example in Javascript

var a = 1;
a = a++;
console.log(a); // 1

var b = 1;
b = ++b;
console.log(b); // 2

var c = 1;
c += 1;
console.log(c); //2

我理解为什么它以这种方式工作以防 b 和 c ，但是 a 呢？
首先，代码进行赋值 a = a ，实际值保持不变，但是它应该（如我所见）增加并增加值<每单位code> a 。但这没有发生。为什么？

I understand why it works this way in case b and c, but what about a? At first the code makes an assignment a = a, the value stays the same actually, but then it should (as I see) make increment and increase value a per unit. But this not happening. Why?

推荐答案

var a = 1;
a = a++;

1. 1 分配给 a


2. a ++ 被评估为 1


3. a ++ 增量 a 到 2


4. a = {以前的评估结果} 将 1 分配给 a 所以它是 1 再次

1. 1 is assigned to a
2. a++ is evaluated as 1
3. a++ increments a to 2
4. a = {result of previous evaluation} assigns the 1 to a so it is 1 again

var b = 1;
b = ++b;

1. 1 分配给 b


2. ++ b 增量 b 到 2


3. + + b 评估为 2


4. b = {先前评估的结果} 将 2 分配给 b 所以它是 2 仍然

1. 1 is assigned to b
2. ++b increments b to 2
3. ++b is evaluated as 2
4. b = {result of previous evaluation} assigns the 2 to b so it is 2 still

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