javascript中++和+ = 1之间的差异 [英] Difference between ++ and +=1 in javascript

问题描述

有人可以解释为什么以下函数会给出不同的结果。第一个似乎不起作用，但第二个确实有效。我很困惑，因为我认为+ = 1而且++做了同样的事情。

Could somebody explain why the following functions give different results. The first does not seem to work, but the second does. I'm puzzled because I thought +=1 and ++ did the same thing.

（我不打算实际使用这段代码，只是为了证明其差异）。

(I'm not intending to actually use this code, it's just to demonstrate the difference).

/*function 1*/
function incrementIfZero1(base,element) {

    if (element == 0) {
        return base++;
    }
    else
    {
        return base;
    }
};


/*function 2*/
function incrementIfZero2(base,element) {

    if (element == 0) {
        return base+=1;
    }
    else
    {
        return base;
    }
};

incrementIfZero1(1,0) /* -> 1*/
incrementIfZero2(1,0) /* -> 2*/

非常感谢任何帮助。

谢谢，

罗宾

感谢您的回复，现在有意义。我也尝试过以下语句，结果与函数1相同：

Thank you for your replies, it makes sense now. I had also tried the following statement, which resulted in the same thing as function 1:

return (base++)

我现在感到惊讶的是，这并没有给出与功能2相同的结果 - 我本来希望括号为'强制'在返回之前对其进行评估。知道为什么不是这种情况吗？

I'm now surprised that this doesn't give the same result as function 2 - I would have expected the brackets to 'force' it to be evaluated before returning. Any idea why this is not the case?

推荐答案

当你 return base ++ 它在增加之前返回base的值。你想做 ++ base 以确保首先发生增量然后返回

when you return base++ it returns the value of base just before it gets incremented. You want to do ++base to make sure the increment happens first then it gets returned

否则 ++ 与相同+ = 1

为了回应你的编辑，我尝试在括号中包装随机语句，并且大多数数学运算符按预期响应，这种增量似乎是免除的，可能是因为预增量与后增量的语法是高度有意的并且语句本身 返回 特定值，无论您是否将其包装在括号中

[edit] in response to your edit, i tried wrapping random statements in parentheses and most mathematical operators respond as expected, this incrementation seems to be exempt, likely because the syntax of pre-incrementation vs post-incrementation is highly intentional and the statement itself returns a specific value regardless of whether or not you wrap it in parentheses

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