How to keep json object with highest value among duplicates with nodejs

Question

I have JSON objects imported from an external system, some of which are duplicates in an ID value. Foe example:

{
"ID": "1",
"name": "Bob",
"ink": "100"
},
{
"ID":"2",
"Name": "George",
"ink": "100"
},
{
"ID":"1",
"name": "Bob",
"ink":"200"
}

I am manipulating the information for each object, then push them into a new JSON array:

var array = {};
array.users = [];

for (let user of users) {
function (user) => {
...
array.users.push(user);
}
}

I need to remove all duplicates save the one with the highest value in the ink key. I found solutions to do this for the array AFTER it is constructed, but that means I use system resources for nothing - no reason to manipulate users that will be removed anyway.

I am looking for a way to check for each new user if a user with that ID:value pair already exists in the array.users[] array, if it does, compare the values of the ink key, if it is higher - remove the existing from the array, then I can continue with my manipulation code and push the new user into the array.

Any ideas of what would be the most elegant/efficient/shortest way to accomplish this?

Sebastian Salletmayer · Accepted Answer · 2022-04-21T10:05:47.353

1

I am not really sure if I fully understood your question. If I understand correctly you don't want to pass through the entire array after it is constructed and check for duplicates?

"If in doubt throw a hash map at the problem". Use a map instead of a plain array. The map key stores the ID. And save your fields as the value. If a key already exists then you can just check which value is higher.

Code example should somewhat look like this:

let userMap = new Map()

for (let user in users) {
   if (userMap.has(user["ID"]) //Look which ink is bigger
   else //Store new entry
}

EDIT: My solution does require an extra step though and is not directly done in the original array. However, I still think that maps are probably one of the most efficient ways to handle this...

edited Apr 21 '22 at 10:05

answered Apr 21 '22 at 09:58

Sebastian Salletmayer

73
7

1

Oh that's great! Thanks! I created a rule like if(!map.get(user.ID) || map.get(user.ID) >= user.ink), which checks both if the map has the user ID and if it is larger, then I can apply the code. Very elegant, thank you. – Nimrod Yanai Apr 21 '22 at 11:33
1

Looks good to me! :) – Sebastian Salletmayer Apr 21 '22 at 11:37

score 0 · Answer 2 · answered Apr 21 '22 at 09:53

var array = {};
array.users = users.filter((user)=>{
  for (let userSecond of users) {
    if(userSecond.id === user.id && +userSecond.ink > +user.ink){
      return false;
    }
  }
  return true;
});

Not the cleanest solution perhaps but it should do the job. Basically you filter through users. Within the filter you go through every user again to check if any of them has the same id and more ink, if so the current user should be discarded by returning false. If no user is found with same id and more ink the current user will stay in the array.

How to keep json object with highest value among duplicates with nodejs

2 Answers2