Javascript Math.min.apply(0, array) - 为什么？

Math.min.apply(0, array) - why?

提问by Trevor Burnham

I was just digging through some JavaScript code (Rapha?l.js) and came across the following line (translated slightly):

我只是在挖掘一些 JavaScript 代码 (Rapha?l.js) 并遇到以下行（略有翻译）：

Math.min.apply(0, x)

where xis an array. Why on earth would you do this? The behavior seems to be "take the min from the array x."

哪里x是一个数组。你到底为什么要这样做？行为似乎是“从数组中取出 min x”。

回答by Trevor Burnham

I realized the answer as I was posting my own question: This isthe most succinct way of taking the min of an array xin JavaScript. The first argument is totally arbitrary; I find the 0 confusing because the code intuitively means "Take the min of 0 and x," which is absolutely not the case. Using the Math object makes more sense for human-readability, but the Raphael.js authors are obsessed with minification and 0 is three bytes shorter.

我在发布自己的问题时意识到了答案：这是x在 JavaScript中获取数组最小值的最简洁方法。第一个论点完全是武断的；我发现 0 令人困惑，因为代码直观地表示“取 0 和 x 的最小值”，这绝对不是这种情况。使用 Math 对象对人类可读性更有意义，但 Raphael.js 作者痴迷于缩小，而 0 更短三个字节。

See http://ejohn.org/blog/fast-javascript-maxmin/

见http://ejohn.org/blog/fast-javascript-maxmin/

For readability's sake, I'd strongly urge people to stop doing this and instead define a function along the lines of

为了可读性，我强烈敦促人们停止这样做，而是按照以下方式定义一个函数

function arrayMin(arr) { return Math.min.apply(Math, arr); };

回答by David Rosson

The reason is this:

原因是这样的：

• Your input xis an array

• The signature of Math.min()doesn't take arrays, only comma separated arguments

• If you were using Function.prototype.call()it would have almost the same signature, except the first argument is the thiscontext, i.e.who's "calling"

  • Example: Math.min.call(context, num1, num2, num3)

• The contextonly matters when you refer to thisinside the function, e.g.most methods you can call on an array: Array.prototype.<method>would refer to this(the array to the left of the 'dot') inside the method.

• Function.prototype.apply()is very similar to .call(), only that instead of taking comma-separated arguments, it now takes an array after the context.

  • Function.prototype.call(context, arg1, arg2, arg3)
  • Function.prototype.apply(context, [arg1, arg2, arg3])

• The 0or nullthat you put in as the first argument is just a place shifter.

• 您的输入x是一个数组

• 的签名Math.min()不接受数组，只接受逗号分隔的参数

• 如果您正在使用Function.prototype.call()它，它将具有几乎相同的签名，除了第一个参数是this上下文，即谁在“调用”

  • 例子： Math.min.call(context, num1, num2, num3)

• 在context只有当你指的事项this里面的函数，例如，你可以在阵列上调用大多数方法：Array.prototype.<method>将引用this（数组左边的“点”）的方法内。

• Function.prototype.apply()与 非常相似.call()，只是它现在不是采用逗号分隔的参数，而是在context.

  • Function.prototype.call(context, arg1, arg2, arg3)
  • Function.prototype.apply(context, [arg1, arg2, arg3])

• 您作为第一个参数放入的0ornull只是一个位置移位器。

回答by Igor Vaschuk

The proper and less confusing way to call this is: Math.min.apply(null, array)

调用它的正确且不那么令人困惑的方法是： Math.min.apply(null, array)

If parameter is unused setting it to null makes code more readable than setting it to 0 or Math

如果参数未使用，则将其设置为 null 会使代码比将其设置为 0 或 Math 更具可读性

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply

回答by Mike Q

Here is an example where we can get the MAX and MIN timezone offsets for the given year for a timezone. It returns the two changes for the year to account for DST and ST. (i.e. ST = 300 an DST = 360 for the timezone in question).

这是一个示例，我们可以获取给定年份的时区的 MAX 和 MIN 时区偏移量。它返回当年的两个变化以说明 DST 和 ST。（即 ST = 300 和 DST = 360 对于相关时区）。

   var arr = [];
   for (var i = 0; i < 365; i++) {
       var d = new Date();
       d.setDate(i);
       var newoffset = d.getTimezoneOffset();
       arr.push(newoffset);
   }
   var DST = Math.min.apply(null, arr);
   var nonDST = Math.max.apply(null, arr);
   tw.local.stInt = DST
   tw.local.edInt = nonDST