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在 JavaScript 中为什么 Math.max() 会比 Math.min() 小？ #6953

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在 JavaScript 中为什么 Math.max() 会比 Math.min() 小？ #6953

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feat: 在 JavaScript 中为什么 Math.max() 会比 Math.min() 小？
zhanght9527 Apr 23, 2020
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feat: 翻译完成
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Expand Up @@ -2,58 +2,57 @@
> * 原文作者：[Dr. Derek Austin 🥳](https://medium.com/@derek_develops)
> * 译文出自：[掘金翻译计划](https://github.com/xitu/gold-miner)
> * 本文永久链接：[https://github.com/xitu/gold-miner/blob/master/TODO1/why-math-max-is-less-than-math-min-in-javascript.md](https://github.com/xitu/gold-miner/blob/master/TODO1/why-math-max-is-less-than-math-min-in-javascript.md)
> * 译者：
> * 校对者：
> * 译者：[zhanght9527](https://github.com/zhanght9527)

# Why Math.max() is Less Than Math.min() in JavaScript
# 在 JavaScript 中为什么 Math.max() 会比 Math.min() 小？

![Photo by [Brett Jordan](https://unsplash.com/@brett_jordan?utm_source=medium&utm_medium=referral) on [Unsplash](https://unsplash.com?utm_source=medium&utm_medium=referral)](https://cdn-images-1.medium.com/max/9196/0*NqSH9Eveu-3BTQ2V)
![图片来自 [Brett Jordan](https://unsplash.com/@brett_jordan?utm_source=medium&utm_medium=referral) on [Unsplash](https://unsplash.com?utm_source=medium&utm_medium=referral)](https://cdn-images-1.medium.com/max/9196/0*NqSH9Eveu-3BTQ2V)

> **Math.max() \< Math.min() === true**

Surprised? Here’s why JavaScript’s maximum function is less than its minimum function when no arguments are passed.
惊讶吗？这就是为什么在不传递参数时，JavaScript 中取最大值函数小于取最小值函数的原因。

Did you know that [`Math.max()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max) with no arguments returns a value that is smaller than [`Math.min()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/min) with no arguments in JavaScript?
你知道在 JavaScript 中 [`Math.max()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max) 不传参数返回的值要比 [`Math.min()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/min) 不传参数返回的值小的原因吗？

```JavaScript
console.log(Math.max() < Math.min()) // true
```

Why is that? Let’s check what the functions return:
为什么会这样？让我们检查一下这个函数返回了什么：

```JavaScript
console.log(Math.max()) // -Infinity
```

That’s weird — [`Infinity`](https://medium.com/swlh/what-is-infinity-in-javascript-%EF%B8%8F-1faf82f100bc) is actually the biggest number in JavaScript, along with the values [`Number.MAX_VALUE`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_VALUE) and [`Number.MAX_SAFE_INTEGER`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER).
很奇怪 —— 在 JavaScript 中 [`Infinity`](https://medium.com/swlh/what-is-infinity-in-javascript-%EF%B8%8F-1faf82f100bc) 实际上是数值最大的数，还有 [`Number.MAX_VALUE`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_VALUE) 和 [`Number.MAX_SAFE_INTEGER`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER).

What does `Math.min()` return with no arguments?
那么 `Math.min()` 不带参数会返回什么呢？

```JavaScript
console.log(Math.min()) // Infinity
```

Again, we have the reverse of what we might expect — [`-Infinity`](https://medium.com/swlh/what-is-infinity-in-javascript-%EF%B8%8F-1faf82f100bc) is the smallest number in JavaScript, along with [`Number.MIN_VALUE`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MIN_VALUE).
又一次，我们所期待的恰恰相反 —— 在 JavaScript 中 [`-Infinity`](https://medium.com/swlh/what-is-infinity-in-javascript-%EF%B8%8F-1faf82f100bc) 应该是数值最小的数，还有 [`Number.MIN_VALUE`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MIN_VALUE).

So why do `Math.min()` and `Math.max()` seem to have it backwards?
那么为什么 `Math.min()` 和 `Math.max()` 实际的值和我们预期的会相反呢？

The answer is buried in the [MDN Docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max#Description):
答案就藏在 [MDN Docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max#Description) ：

> “[`-Infinity`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity) is the initial comparant because almost every other value is bigger, that's why when no arguments are given, -[`Infinity`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity) is returned.
> “[`-Infinity`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity) 是初始比较项，因为几乎所有其他值都比它更大，这就是为什么没有给出参数的时候，会返回 -[`Infinity`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity)。
>
> If at least one of arguments cannot be converted to a number, the result is [`NaN`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/NaN).” — [MDN Docs for `Math.max()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max#Description)
> 如果至少有一个参数让其不能转换为一个数字，那么结果将是 [`NaN`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/NaN).” — [`Math.max()` 在 MDN 中的文档](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max#Description)

Of course! `Math.max()` is just an implementation of a `for` loop over the parameters (check out [the actual Chrome V8 implementation](https://github.com/v8/v8/blob/cd81dd6d740ff82a1abbc68615e8769bd467f91e/src/js/math.js#L77-L102)).
当然了！ `Math.max()` 只是一个基于 `for` 循环的参数实现 （看看 [Chrome V8 的实现](https://github.com/v8/v8/blob/cd81dd6d740ff82a1abbc68615e8769bd467f91e/src/js/math.js#L77-L102)）。

So, `Math.max()` starts with a search value of `-Infinity`, because any other number is going to be greater than -Infinity.
因此，`Math.max()` 会从 `-Infinity` 开始搜索，因为任何其他数字都比 `-Infinity` 大。

Similarly, `Math.min()` starts with the search value of `Infinity`:
同样，`Math.min()` 会从 `Infinity` 开始搜索：

> “If no arguments are given, the result is [`Infinity`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity).
> “如果没有传任何参数，那么将返回 [`Infinity`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity)。
>
> If at least one of arguments cannot be converted to a number, the result is [`NaN`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/NaN).” — [MDN Docs for `Math.min()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/min#Description)
> 如果至少有一个参数不能转换为数字，那么将返回 [`NaN`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/NaN)。” — [MDN Docs for `Math.min()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/min#Description)

[The ECMAScript Specification](https://www.ecma-international.org/ecma-262/10.0/index.html#sec-math.max) for `Math.max()` and `Math.min()` also points out that `+0` is considered to be larger than `-0` by these functions:
[ECMAScript 规范](https://www.ecma-international.org/ecma-262/10.0/index.html#sec-math.max) 中对于 `Math.max()` 和 `Math.min()`也指出，通过这些函数，`+0` 被认为大于 `-0`：

```JavaScript
console.log(Math.max(+0,-0)) // 0
Expand All @@ -65,16 +64,16 @@ console.log(+0 == -0) // true
console.log(Object.is(+0,-0)) // false
```

That behavior is different than the [`>` greater than and `\<` less than operators](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Relational_operators), which consider `-0` [negative zero](https://medium.com/coding-at-dawn/is-negative-zero-0-a-number-in-javascript-c62739f80114) to be equal to `+0` positive zero.
这种行为不同于 [`>` 大于和 `\<` 小于运算符](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Relational_operators)，后者认为 `-0` [负零](https://medium.com/coding-at-dawn/is-negative-zero-0-a-number-in-javascript-c62739f80114) 等于 `+0` 正零。

Technically, `-0` negative zero is equal to `0` positive zero according to [the `==` and `===` equality operators,](https://medium.com/better-programming/making-sense-of-vs-in-javascript-f9dbbc6352e3) but not according to [`Object.is()`](https://medium.com/coding-at-dawn/es6-object-is-vs-in-javascript-7ce873064719).
从技术上讲，根据 [`==` 和 `===` 相等运算符](https://medium.com/better-programming/making-sense-of-vs-in-javascript-f9dbbc6352e3) `-0` 负零是和 `0` 正零相等的，而不是根据 [`Object.is()`](https://medium.com/coding-at-dawn/es6-object-is-vs-in-javascript-7ce873064719)。

So, in a sense, `Math.max()` and `Math.min()` are smarter for `-0` negative zero than a naive implementation ([see lines 96–99 in the V8 code](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Relational_operators)).
因此，在某种意义上，`Math.max()` 和 `Math.min()` 比 `-0` 负零单纯的实现更加地优雅（[参见V8代码中的第 96-99 行](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Relational_operators)）。

Like this article? Then you’ll like my article on the fastest way to [find the min and max in a JavaScript array](https://medium.com/coding-at-dawn/the-fastest-way-to-find-minimum-and-maximum-values-in-an-array-in-javascript-2511115f8621) — where I show a method of using `Math.max()` and `Math.min()` that is much faster than using the [`...` spread operator](https://medium.com/coding-at-dawn/how-to-use-the-spread-operator-in-javascript-b9e4a8b06fab):
[**The Fastest Way to Find Minimum and Maximum Values in an Array in JavaScript**](https://medium.com/coding-at-dawn/the-fastest-way-to-find-minimum-and-maximum-values-in-an-array-in-javascript-2511115f8621)
喜欢这篇文章吗？ 那么你会喜欢我的这篇文章：用最快的方式[在 JavaScript 数组中找到最大和最小值](https://medium.com/coding-at-dawn/the-fastest-way-to-find-minimum-and-maximum-values-in-an-array-in-javascript-2511115f8621) —— 我展示了一个使用 `Math.max()` 和 `Math.min()` 的方法，比使用 [`...` 扩展运算符](https://medium.com/coding-at-dawn/how-to-use-the-spread-operator-in-javascript-b9e4a8b06fab) 更快：
[**用最快的方法在 JavaScript 中查找数组中最小值和最大值**](https://medium.com/coding-at-dawn/the-fastest-way-to-find-minimum-and-maximum-values-in-an-array-in-javascript-2511115f8621)

Now you know all the quirks of `Math.max()` and `Math.min()`!
现在你已经了解了 `Math.max()` 和 `Math.min()` 的所有特性！

Happy Coding! 😊💻😉🔥🙃

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