因为所有问题都已经在截图里，所以就不另外说了。

这个题目我想了一天都没想出来，后来有个群的朋友告诉我这个方法。这个代码也是他写好的，我大致弄懂了思路，但还是想不明白为什么return的数组，不是ints[i]在前面。我试过了，如果把return的数组两个元素对调，就无法通过检测。

图片不够清晰，还是把详情写一下吧。

题目大意：

Sum of Pairs

Given a list of integers and a single sum value, return the first two values (parse from the left please) in order of appearance that add up to form the sum.

示例：

sum_pairs([11, 3, 7, 5],         10)
#              ^--^      3 + 7 = 10
== [3, 7]

sum_pairs([4, 3, 2, 3, 4],         6)
#          ^-----^         4 + 2 = 6, indices: 0, 2 *
#             ^-----^      3 + 3 = 6, indices: 1, 3
#                ^-----^   2 + 4 = 6, indices: 2, 4
#  * entire pair is earlier, and therefore is the correct answer
== [4, 2]

sum_pairs([0, 0, -2, 3], 2)
#  there are no pairs of values that can be added to produce 2.
== None/nil/undefined (Based on the language)

sum_pairs([10, 5, 2, 3, 7, 5],         10)
#              ^-----------^   5 + 5 = 10, indices: 1, 5
#                    ^--^      3 + 7 = 10, indices: 3, 4 *
#  * entire pair is earlier, and therefore is the correct answer
== [3, 7]

我提交的代码：

var sum_pairs=function(ints, s){
    //your code here
  var set=new Set();
  for(var i=0;i