i = i ++和i = i + 1之间的差异 [英] Difference between i = i++ and i = i + 1

问题描述

https://www.hackerrank.com/challenges/compare-the-triplets

var alice = bob = 0;
if(a0 > b0){
  alice = alice + 1;
} else if (a0 < b0) {
  bob = bob + 1;
} else if (a1 > b1) {
  alice = alice + 1;
} else if (a1 < b1) {
  bob = bob + 1;
} else if (a2 > b2) {
  alice = alice + 1;
} else if (a2 < b2) {
  bob = bob + 1;
}

console.log(alice, bob);

VS

var alice = bob = 0;
if(a0 > b0){
  alice = alice++;
  console.log(alice);
} else if (a0 < b0) {
  bob = bob++;
} else if (a1 > b1) {
  alice = alice++;
} else if (a1 < b1) {
  bob = bob++;
} else if (a2 > b2) {
  alice = alice++;
} else if (a2 < b2) {
  bob = bob++;
}

console.log(alice, bob);

第一个正常工作但第二个没有。有人可以帮助我两者之间有什么区别吗？

first one worked properly but the second one didn't. Can someone help me what are the differences between the two?

推荐答案

那是因为第一次一个为变量分配一个新值，而第二个返回并递增它。

That is because the first one assigns a new value to the variable, while the second one returns and increments it.

这是一个简单的变量赋值，其中 a + 1 的值分配给 A 。执行此行后， a 将增加1。

This is a simple variable assignment, where the value of a + 1 is assigned to a. After this line executes, a will be incremented by one.

这是增量运算符。它不仅将变量递增1，还返回其值。

This is the increment operator. It not only increments the variable by 1, but also returns its value.

• ++ a 称为预增量。它将 a + 1 的值分配给 a ，然后返回 a <的值/ code>。


• a ++ 称为后增量。它首先返回 a 的值，然后将 a + 1 分配给 A 。

• ++a is called pre-increment. It assigns the value of a + 1 to a, then returns the value of a.
• a++ is called post-increment. It first returns the value of a, then assigns a + 1 to a.

这是您看到的错误的原因。这意味着在您的初始示例中，这是您的代码中发生的情况：

This is the cause for the error you're seeing. It means that in your initial example, this is what happens in your code:

alice = alice++; // assings the original value of alice to alice, then increments it
  console.log(alice); // still the initial value

通过预先递增变量，您将得到：

By pre-incrementing the variable, you would get:

alice = ++alice; // assings alice+1 to alice
  console.log(alice); // now contains the value of alice+1

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