Add attributes to object using array

Question

how can I add several attributes to a sub-sub-object in ES6 by using the keys of objects from an array ?

I have this:

const data = [{
    id: 'abc-test',
  },
  {
    id: 'xyz-test',
  },
];




const t = {
  a: {
    filters: {
      tOne: [],
    }
  }

};

The result should look like this:

const t = {
  a: {
    filters: {
      tOne: [],
      'abc-test': [],
      'xyz-test': [],
    }
  }

};

What I tried

...data.map((el) => [el.id]),

How to solve it ? I know that this could be done by using .forEach but I would like to use another ES6 Array.prototype functions if possible.

What do you mean by "I know that this could be done by using .forEach but I would like to use ES6 Array.prototype functions if possible."? forEach is an "Array.prototype" function like any other. — ibrahim mahrir
– ibrahim mahrir, Commented Nov 18, 2019 at 0:24
Sorry, forgot the word "another" in my description. See updated description. — Gutelaunetyp
– Gutelaunetyp, Commented Nov 18, 2019 at 0:27
forEach is really the best choice here. The other functions have other usages. I mean you can use reduce like data.reduce((acc, o) => (acc[o.id] = [], acc), t.a.filters) or use map as a forEach, but that would be like using a shoe to spread butter on a piece of bread, you can do it, but why would you do that when you have a knife/forEach?!! — ibrahim mahrir
– ibrahim mahrir, Commented Nov 18, 2019 at 1:50

ibrahim mahrir · Accepted Answer · 2019-11-18 01:55:09Z

2

forEach is an Array function (or as you like to call it: an Array.prototype function). Among all the other Array functions, forEach is the best fit for what you need. The other ones have other usages.

So, simply use forEach to loop over the objects in the array and assign the properties directly to t.a.filters:

data.forEach(o => t.a.filters[o.id] = []);

Example:

const data = [ { id: 'abc-test' }, { id: 'xyz-test' } ];

const t = { a: { filters: { tOne: [] } } };

data.forEach(o => t.a.filters[o.id] = []);

console.log(t);

edited Nov 18, 2019 at 1:55

answered Nov 18, 2019 at 0:15

ibrahim mahrir

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4 Comments

Nick Over a year ago

Likely doesn't get better than this!

ibrahim mahrir Over a year ago

@Nick I think your answer is valid giving that OP clearly doesn't want to use forEach. You may consider undeleting your answer.

Nick Over a year ago

Sure, I undeleted it, but I'm not a fan of doing things inefficiently, which my solution is compared to yours

ibrahim mahrir Over a year ago

@Nick Ehem, you mean like using a shoe to spread butter lol

Nick · Accepted Answer · 2019-11-18 00:12:31Z

1

I would use a combination of reduce and the spread operator.

const data = [{
    id: 'abc-test',
  },
  {
    id: 'xyz-test',
  },
];

const t = {
  a: {
    filters: {
      tOne: [],
    }
  }

};

const newKeys = data.reduce((acc, el) => {
  acc[el.id] = [];
  return acc;
}, {});

t.a.filters = {
  ...t.a.filters,
  ...newKeys
};

console.log(t);

answered Nov 18, 2019 at 0:12

Nick

16.7k3 gold badges21 silver badges38 bronze badges

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