在对象数组中添加匹配键的值 [英] Add values of matching keys in array of objects

问题描述

我有一个包含许多具有匹配键的对象的数组：

I have an array with a number of objects with matching keys:

[{a: 2, b: 5, c: 6}, {a:3, b: 4, d:1},{a: 1, d: 2}]

我想循环遍历数组，如果键匹配，我想添加每个键的结果，并返回一个具有每个键之和的对象。

I want to loop through the array and if the keys match I want to add the results of each and return one object with the sum of each key.

即

{a: 6, b: 9, c: 6, d: 3}

我目前的代码是

function combine() {
   var answer = [];
  for(var i in arguments){
    answer.push(arguments[i])
  }

 answer.reduce(function(o) {
    for (var p in o)
        answer[p] = (p in answer ? answer[p] : 0) + o[p];
        return answer;
    }, {});
}

我可以找到答案 here 如果我要使用下划线库，但是我希望这样做它没有使用库。我想我很难理解 reduce 方法是如何工作的 - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

I can find the answer here if I was to use the underscore library, however I wish to do it without using a library. I think I am having difficulty understanding how the reduce method works - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

如何解决这个问题的任何帮助将不胜感激。此外，我觉得这是一个答案应该是在某个地方，而不必使用库。

Any help as to how to solve this would be greatly appreciated. Also, I feel it is an answer that should be somewhere on SO without having to use a library.

提前致谢。

推荐答案

遍历每个对象并添加它。

Loop through each object and add it.

    var a = [{a: 2, b: 5, c: 6}, {a:3, b: 4, d:1},{a: 1, d: 2}];
    var ans = {};

    for(var i = 0; i < a.length; ++i){
      for(var obj in a[i]){
       ans[obj] = ans[obj] ? ans[obj] + a[i][obj] : a[i][obj];
      }
    }
document.write(JSON.stringify(ans));

ans[obj] = ans[obj] ? ans[obj] + a[i][obj] : a[i][obj];

This line is the same as    
// check if the object already exists(or not falsy) in answer, if Yes add that value to the new value
if(ans[obj])
{
  ans[obj] = ans[obj] + a[i][obj];
}
// else create a new object in the answer and set it to the value from the array
else
{
  ans[obj] = a[i][obj];
}

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