How to sort array by object property with multiple conditions in Javascript

Question

I've been reading similar solved problems but couldn't understand how to apply it in my case.

So, I have an unsorted array of objects:

const queues = [
  {"floor":2,"direction":"REQUEST_FLOOR"},
  {"floor":1,"direction":"REQUEST_FLOOR"},
  {"floor":5,"direction":"CALL_DOWN"},
  {"floor":8,"direction":"CALL_DOWN"},
  {"floor":7,"direction":"REQUEST_FLOOR"},
  {"floor":6,"direction":"CALL_DOWN"}
];

I'd like to sort it into:


const queues = [
  {"floor":1,"direction":"REQUEST_FLOOR"},
  {"floor":2,"direction":"REQUEST_FLOOR"},
  {"floor":7,"direction":"REQUEST_FLOOR"},
  {"floor":8,"direction":"CALL_DOWN"},
  {"floor":6,"direction":"CALL_DOWN"},
  {"floor":5,"direction":"CALL_DOWN"},
];

So, the priority rules I want to apply are :

Sort "REQUEST_FLOOR" first then only "CALL_DOWN".
Sort "REQUEST_FLOOR" in ascending and "CALL_DOWN" in descending.

I'm able to make it work by separating it into 2 different arrays, sort, then combine it at the end. Here is my code:

const requestFloors = queues.filter(queue => queue.direction === "REQUEST_FLOOR");
const callDownFloors = queues.filter(queue => queue.direction === "CALL_DOWN");
requestFloors.sort((a,b) => a.floor - b.floor);
callDownFloors.sort((a,b) => b.floor - a.floor);
const newQueues = [...requestFloors,...callDownFloors];

Question: Instead of filtering + sorting, I'd like to just use sort(), so maybe something like this: queues.sort((a,b) => b.direction.localeCompare(a.direction) || a.floor - b.floor ); However, this code sort the the direction correctly, but the problem is it still sorts the floor in ascending for both direction.

How do I achieve the same result by only using sort()? Any helps will be greatly appreciated.

Alberto · Accepted Answer · 2020-07-13 14:06:52Z

2

You can use the sort function:

queues.sort((el1, el2) => {
     if(el1.direction ==  el2.direction){
         if(el1.direction === "REQUEST_FLOOR")
            return el1.floor - el2.floor 
         else 
            return el2.floor - el1.floor
     } 
     else if(el1.direction === "REQUEST_FLOOR") 
         return -1;
     else 
         return 1;
})

Output:

[
   {
      "floor":1,
      "direction":"REQUEST_FLOOR"
   },
   {
      "floor":2,
      "direction":"REQUEST_FLOOR"
   },
   {
      "floor":7,
      "direction":"REQUEST_FLOOR"
   },
   {
      "floor":8,
      "direction":"CALL_DOWN"
   },
   {
      "floor":6,
      "direction":"CALL_DOWN"
   },
   {
      "floor":5,
      "direction":"CALL_DOWN"
   }
]

edited Jul 13, 2020 at 14:06

answered Jul 13, 2020 at 13:58

Alberto

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6 Comments

Bergi Over a year ago

A comparison function should not return a boolean in javascript

Alberto Over a year ago

@Bergi thank you for the warning edited, the answer

Alberto Over a year ago

@Leomord can you please try again? i've changed the code

Bergi Over a year ago

el1.floor + el2.floor should be el2.floor - el1.floor though :-)

Alberto Over a year ago

@Bergi ahah i was just right editing the answer, thank you again

|

Bergi · Accepted Answer · 2020-07-13 13:58:32Z

1

If the direction is the same in both compared items, you can conditionally choose the evaluation of the other columns based on the direction:

queues.sort((a,b) =>
  (a.direction=="CALL_DOWN") - (b.direction=="CALL_DOWN") ||
  (a.direction == "CALL_DOWN"
    ? b.floor - a.floor
    : a.floor - b.floor)
);

answered Jul 13, 2020 at 13:58

Bergi

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2 Comments

Leomord Over a year ago

May I know why u choose to use the == instead of the strict equality === ?

Bergi Over a year ago

@Leomord Because it does not matter when comparing values of the same type (both are strings)

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