Sorting a JSON by value of a dynamic name property

Question

I've been trying to do an online coding excericise, the excercise look like this :

A json array A has a random number objects that contains a key and a double value. The array A may have up to 10000 objects. Ex: A = [{"a": 2.0},{"a": 2.7},{"c": 2.0},{"b": 5.1},{"d": 2.9},{"c": 2.0},{"f": 2.2},{"h": 2.1}]

Another array B has a random set of sum operations executed with the keys. The value of those keys can be found in A. If the key is not presented in A, so its value is zero. Ex: B = ["a+b","b+d+f","k+z"]

Your job is to combine the arrays B and A, providing an array C that contains the results of the sum operations of B. The resulting array must be sorted in a descending order. Combining the examples above, the resulting array would be: Ex: C = [ {"b+d+f": 10.2}, {"a+b": 9.8}, {"k+z": 0} ]

The code looks like this (please let me know if there is any better implementation whit a smaller O())

var a = [{"a": 2.0},{"a": 2.7},{"c": 2.0},{"b": 5.1},{"d": 2.9},{"c": 2.0},{"f": 2.2},{"h": 2.1}]
var b = ["a+b","b+d+f","k+z"];
var c = [];

function sumArrays(){ 
 for (var sum in b){
  var keysToSum = b[sum].split("+");
  var sumatory = 0;
  for(var key in keysToSum){   
   for(var number in a){
    if(a[number].hasOwnProperty(keysToSum[key])){
     sumatory += a[number][keysToSum[key]];
    }
   }
  }

  c.push(JSON.parse("{\"" + b[sum] + "\":" + sumatory + "}"));
 }

 //c.sort(function(a,b){
 // return a.value - b.value;
 //});
}

I can't get the array C sorted, because the property name changes. Any ideas?

Thanks !

quick fix something like `a[Object.keys(a)[0]] -b[Object.keys(b)[0]]` — Grundy, Aug 07 '15 at 18:14
do you know that in `A` array you have an objects with duplicated property name, i mean `{"a": 2.0},{"a": 2.7}` and others? what value should be used in this case? — Grundy, Aug 07 '15 at 18:16
i suggest not use [for..in loop with array](http://stackoverflow.com/questions/500504/why-is-using-for-in-with-array-iteration-such-a-bad-idea) — Grundy, Aug 07 '15 at 19:24

score 1 · Accepted Answer · answered Aug 07 '15 at 18:44

1

First you need the first value of an object:

function firstValue(obj){
   for(var prop in obj){
      return obj[prop];
   }
}

then use it for sort

a.sort(function(a,b){ return firstValue(a)-firstValue(b)})

answered Aug 07 '15 at 18:44

Emilio Platzer

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Sorting a JSON by value of a dynamic name property

1 Answers1