Sum javascript object propertyA values with same object propertyB in array of objects

Question

How would one take a javascript array of objects such as:

my objArr = [
{key:Mon Sep 23 2013 00:00:00 GMT-0400, val:42},
{key:Mon Sep 24 2013 00:00:00 GMT-04         


        

Answer 1

You should be assigning each object not found to the result with its .key property.

If it is found, then you need to add its .val.

var temp = {};
var obj = null;
for(var i=0; i < objArr.length; i++) {
   obj=objArr[i];

   if(!temp[obj.key]) {
       temp[obj.key] = obj;
   } else {
       temp[obj.key].val += obj.val;
   }
}
var result = [];
for (var prop in temp)
    result.push(temp[prop]);

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Also, part of the problem was that you were reusing the item variable to reference the value of .key, so you lost reference to the object.