JavaScript: De-duplicate and Count Properties of Array

Question

Working with arrays is definitely one of my weakest area, so any help is greatly appreciated. 😊

To add to the challange, this is for a WebOS application that has the following limitations ...

JavaScript 5.0
Only extra library is JQuery
No arrow functions (=>)

Example of received array ...

var Schedule = [{
  "category": "Laboratory", "status": "COMPLETE" }, {
  "category": "Radiology" , "status": "COMPLETE" }, {
  "category": "Laboratory", "status": "SCHEDULED"}, {
  "category": "Laboratory", "status": "COMPLETE" }, {
  "category": "Radiology" , "status": "SCHEDULED"}, {
  "category": "Laboratory", "status": "COMPLETE" }, {
  "category": "Doppler"   , "status": "SCHEDULED"
}]

Desired conversion ...

var ScheduleFormatted = [{
  "category": "Laboratory", "complete": "3", "total": "4" }, {
  "category": "Radiology" , "complete": "1", "total": "2" }, {
  "category": "Doppler"   , "complete": "1", "total": "1" }, {
}]

It would be especially great to have the incomplete categories listed first.

I've been successful in achieving parts of this (like getting unique properties, or instance count by status), but the complexity of this has me completely stumped.

Please help.

@NinaScholz -- What success I've had has been limited, but you're welcome to take a look: jsfiddle.net/MangaX/d7vx5a93 — Dustin Halstead
– Dustin Halstead, Commented Apr 18, 2020 at 21:03
Please edit that into the question, then it's worth reopening. Also you can ping me here with @Jonas ... but digging up my email also works :) — Jonas Wilms
– Jonas Wilms, Commented Apr 18, 2020 at 21:51
@JonasWilms -- LOL! Sorry about that. Appreciate you taking a second look, and especially for the help. — Dustin Halstead
– Dustin Halstead, Commented Apr 20, 2020 at 10:44

Jonas Wilms · Accepted Answer · 2020-04-20 11:08:22Z

1

You could create lookup objects where you store the total / completed count for each category:

 var total = {}, complete = {};

 Schedule.forEach(function(item) {
    var c = item.category;
    total[c] = (total[c] || 0) + 1;
    if(item.status === "COMPLETED") 
      complete[c] = (complete[c] || 0) + 1;
 });

 var ScheduleFormatted = Object.keys(total).map(function(category) {
    return { 
     category: category, 
     total: "" + total[category],
     complete: "" + (complete[category] || 0)
   };
 });

edited Apr 20, 2020 at 11:08

answered Apr 18, 2020 at 22:03

Jonas Wilms

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2 Comments

Dustin Halstead Over a year ago

That is an absolutely perfect solution! Thank you good sir. :) The only change I made was to add the following check before the return ... if (complete[category] == undefined) { complete[category] = 0; } ... Appreciate the help so very much.

Dustin Halstead Over a year ago

I see that you updated the answer to address the "complete" amount returning as "undefined" -- and in a much more elegant way than the "if" statement I included. Thank you again.

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