JavaScript IE 9:自定义排序功能 [英] JavaScript IE 9: Custom sort function

问题描述

在IE 9中，如果我在控制台中键入以下内容:

In IE 9, if I type this in the console:

[1, 4, 2, 3].sort(function (a, b) { return a < b; });

结果数组为:[1, 4, 2, 3].

如果我在FF/Chrome中执行此操作，则会得到反向排序的[4, 3, 2, 1].

If I do this in FF/Chrome, I get it, reverse-sorted: [4, 3, 2, 1].

这怎么在IE中不起作用?

How come this doesn't work in IE?

是否有一个抽象这些浏览器差异的函数?换句话说，有没有我可以通过的函数function(a，b){return a< b; }并在所有浏览器中获得相同的结果?有开源的东西吗?

推荐答案

也许是因为如果a较小，则函数应返回-1；如果相等，则返回0；如果1 >较大(反之亦然). 实际上，它必须为零，为正数或负数(如@pimvdb所指出的，这就是我在下面的示例中所使用的).但是，您的函数将永远不会返回-1，这可能会导致问题.

Maybe because the function is supposed to return -1 if a is smaller, 0 if they are equal, and 1 if a is larger (or vice versa if you want reverse order). In fact, it must be zero, a positive or negative number (as @pimvdb pointed out, and that's what I make use of in the example below). Your function will never return -1 though and that might create problems.

请考虑1和3.您的函数为1 < 3返回1，可以，但是为3 < 1返回0.在一种情况下，数字不同，而在另一种情况下，您说的是相等.

Consider 1 and 3. Your function returns 1 for 1 < 3, which is ok, but returns 0 for 3 < 1. In one case the number are different, in the other you are saying that they are equal.

FF/Chrome以相反的顺序对其进行排序可能是由于他们使用的排序算法所致.

That FF/Chrome sort it in reverse order might be due to the sorting algorithm they are using.

尝试:

[1, 4, 2, 3].sort(function (a, b) { return b - a; });

更新:要证实这一点，我们可以看一下规范

Update: To substantiate this, we can have a look at the specification, Section 15.4.4.11 Array.prototype.sort(comparefn), where the properties are given which have to be fulfilled by a comparison function:

如果所有值 a ， b都满足以下所有要求，则函数 comparefn 是针对一组值S的一致比较函数. 和 c (可能是相同的值)在集合S中:符号 a < _CF b 表示 comparefn(a，b)< 0; a = _CF b 表示 comparefn(a，b) = 0(任一符号)；和 a > _CF b 表示 comparefn(a，b)> 0.

A function comparefn is a consistent comparison function for a set of values S if all of the requirements below are met for all values a, b, and c (possibly the same value) in the set S: The notation a <_CF b means comparefn(a,b) < 0; a =_CF b means comparefn(a,b) = 0 (of either sign); and a >_CF b means comparefn(a,b) > 0.

当给定特定的一对值 a 和 b 时，调用
• comparefn(a，b)总是返回相同的值v论点.此外，类型( v )是数字，而 v 不是 NaN .请注意，这暗示着 a < _CF b 中的一个， a = _CF b 和 a > _CF b a 和 b 对，em>都是正确的.
• 调用 comparefn(a，b)不会修改 this 对象.
• a = _CF a (自反)
• 如果 a = _CF b ，则 b = _CF a (对称)
• 如果 a = _CF b 和 b = _CF c ，然后是 a = _CF c (传递性= _CF )
• 如果 a < _CF b 和 b < _CF c ，然后是 a < _CF c (可传递性<< _CF )
• 如果 a > _CF b 和 b > _CF c ，然后是 a > _CF c (> _CF 的传递性)

• Calling comparefn(a,b) always returns the same value v when given a specific pair of values a and b as its two arguments. Furthermore, Type(v) is Number, and v is not NaN. Note that this implies that exactly one of a <_CF b, a =_CF b, and a >_CF b will be true for a given pair of a and b.
• Calling comparefn(a,b) does not modify the this object.
• a =_CF a (reflexivity)
• If a =_CF b, then b =_CF a (symmetry)
• If a =_CF b and b =_CF c, then a =_CF c (transitivity of =_CF)
• If a <_CF b and b <_CF c, then a <_CF c (transitivity of <_CF)
• If a >_CF b and b >_CF c, then a >_CF c (transitivity of >_CF)

注意:上述条件对于确保 comparefn 将集合S划分为等价类并确保这些等价类完全有序是必要的.

NOTE The above conditions are necessary and sufficient to ensure that comparefn divides the set S into equivalence classes and that these equivalence classes are totally ordered.

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