Javascript map within filter

Question

I am trying to add a property (score) to my units array. Scores is an array of object that contains a common id with units.

 this.units.map(unit => {
              unit.score = scores
              .filter(score => unit.id === score.unit_id);
 });

The objects that are contained in the array.

 scores
    {
      unit_id: 1234,
      score: 12,
    }


 this.units
  [
    {
      id: 1234,
      type: 'maths',

    }
   {
      id: '5678',
      type: 'maths',

    }
  ]

It looks ok. Is it because unit.id is not available in the filter?

Now you have edited the code in your question so it works, so what is the question? — James
– James, Commented Aug 24, 2018 at 10:32

Exceptional NullPointer · Accepted Answer · 2018-08-24 10:21:36Z

2

I think this is what you are after. Score does not have a unit_id property, only id.

var scores = [{
  unit_id: 1234,
  score: 12,
}];
var units = [{
  id: 1234,
  type: 'maths',
}, {
  id: 5678,
  type: 'maths',
}];

units.map(unit => {
  unit.score = scores
    .filter(score => unit.id === score.unit_id);
});

console.log(units);

answered Aug 24, 2018 at 10:21

Exceptional NullPointer

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2 Comments

LeBlaireau Over a year ago

Thanks, I was almost there I think I just went round in circles a bit.

Jeremy Thille Over a year ago

You shouldn't be using .map for this, because it doesn't return any value. Use .forEach instead.

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