Combining objects with same key into one object in the array - Typescript

Issue

I have this array Arr = [{ code: "code1", id: "14", count: 24}, {code: "code1", id: "14", count: 37}]

I want to get this Arr = [{ code: "code1", id: "14", count: 61}]

Note: all fields in the objects I want to combine are same except count which is the field I want to sum.

Solution

You can do it like this:

// create new array that will keep your new objects:
var newArray = [];
// iterate over objects in original array:
this.originalArray.forEach((item) => {
   // create new object that you *might* push into new array;
   // use 'id' property of the current item in iteration:
   var newItem = { id: item.id, code: null, count: 0 };
   // iterate again over original array's objects to compare
   // each of them with the current item from upper iteration:
   this.originalArray.forEach((innerItem, i) => {
      // check if they have the same id:
      if (innerItem.id == item.id) {
         // if they do, set values of a new object by adding 
         // the count values
         newItem.count = newItem.count + innerItem.count;
         // and setting the code to be the same as in item from upper iteration
         newItem.code = item.code;
      }
   });
   // push new object to new array only if the new array doesn't already have
   // an item with that id:
   if (!newArray.some((x) => x.id == newItem.id)) newArray.push(newItem);
});
console.log(newArray);

I guess you can have any number of items with the same id in your array, so this works for that too.

STackblitz example: https://stackblitz.com/edit/angular-ivy-1hkspy

Answered By - Misha Mashina