How to count unique value from object of array in javascript

Question

I want to calculate number of unique value and put that in new array. I have below array:

[
  { CategoryId: \"b5c3f43f941c\", CategoryName: \"Category 1\", Categ         


        

Answer 1

You can sort the array first then count the duplicates. The downside is it will modify the original yourArray due to being sorted, so use with caution.

yourArray.sort((a, b) => {
  if (a.CategoryName > b.CategoryName) {
    return 1;
  }
  if (a.CategoryName < b.CategoryName) {
    return -1;
  }
  return 0;
});

var pivot = yourArray[0];
pivot.count = 0;
var counted = [pivot];
yourArray.forEach(item => {
  if (item.CategoryId === pivot.CategoryId) {
    pivot.count++;
  } else {
    pivot = item;
    pivot.count = 1;
    counted.push(pivot);
  }
});