Node.js Filter array of objects where a value is duplicated but another is not

Question

I have an array of objects with the following structure:

[ { type: 'A', rank: 10 }, { type: 'B', rank: 10 }, { type: 'A', rank: 16 }, { type: 'B', rank: 16 } ]

I'd like to keep 1 object per object.type, that one where the object.rank is the biggest, so my expected output in this case is:

[ { type: 'A', rank: 16 }, { type: 'B', rank: 16 } ]

My code is:

conditions = conditions.filter((cond, index, self) => self.findIndex((t) => {return t.type === cond.type && t.rank < cond.rank; }) === index);

This code removes all of the objects. When I don't use the

t.rank < cond.rank

then it works but there is no guarantee it will gives back the biggest rank.

Thank you in advance, of course I don't insist to an ES6 solution.

31piy · Accepted Answer · 2017-11-10 10:31:30Z

2

You can use a combination of Array.reduce and Array.findIndex to get the desired results.

const conditions = [{
  type: 'A',
  rank: 10
}, {
  type: 'B',
  rank: 10
}, {
  type: 'A',
  rank: 16
}, {
  type: 'B',
  rank: 16
}];

const transformed = conditions.reduce((result, item) => {
  const itemIdx = result.findIndex(condition => condition.type === item.type && condition.rank < item.rank);

  if (itemIdx !== -1) {
    result.splice(itemIdx, 1, item);
  } else {
    result.push(item);
  }

  return result;
}, []);

console.log(transformed);

edited Nov 10, 2017 at 10:31

answered Nov 10, 2017 at 10:20

31piy

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2 Comments

Paxi Over a year ago

Thank you for the answer. I made my own based on your answer. The only problem was it is not worked with other inputs (when the order is different). I added an extra condition into the else case:

if (itemIdx !== -1) {             result.splice(itemIdx, 1, item);         } else {             var typeExists = result.findIndex(condition => condition.type === item.type);             if (typeExists === -1) {                 result.push(item);             }         }

31piy Over a year ago

@Paxi -- Please include the additional requirements in your question. This solution was as per your current requirements.

Paras Wadhwa · Accepted Answer · 2017-11-10 13:23:40Z

I made up my own solution using simple javascript functions.

  var conditions = [{ type: 'A', rank: 10 }, { type: 'B', rank: 10 }, { type: 'A', rank: 16 }, { type: 'B', rank: 16 }];

    function check(type, rank) {    
           for (var j = 0; j < conditions.length; j++) {   
            if (conditions[j].type == type) {   
                if (conditions[j].rank > rank) {  
                    return 1;  
                }  
            }  
        }  
        return 0;  
    } 

    for (var i = 0; i < conditions.length; i++) {
        if (check(conditions[i].type, conditions[i].rank)) {
            conditions.splice(i, 1);
            i = i - 1;
        }
    }
    console.log(conditions);

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