reduce/filter array of objects by object key

Question

Consider the following array of objects

const data = [{
    name: 'James',
    sex: 'male',
  }, {
    name: 'Mike',
    sex: 'male',
  }, {
    name: 'Janet',
    sex: 'female',
  }, {
    name: 'Mary',
    sex: 'female',
}];

I'd like to return the following:

{
  males: [{
    name: 'James',
    sex: 'male',
  }, {
    name: 'Mike',
    sex: 'male',
  }]
  females: [{
    name: 'Janet',
    sex: 'female',
  }, {
    name: 'Mary',
    sex: 'female',
}]
}

I've tried mapping over the array, selecting objects by key then adding them to a new array, the result being two arrays. From there, I don't know how to go about returning them in a new object in a succinct way.

I'm not too familiar with the array filter/reduce methods in ES6, would they be useful here? Any help is appreciated!

Eddie · Accepted Answer · 2018-05-10 10:08:21Z

2

You can use reduce

const data = [{
  name: 'James',
  sex: 'male',
}, {
  name: 'Mike',
  sex: 'male',
}, {
  name: 'Janet',
  sex: 'female',
}, {
  name: 'Mary',
  sex: 'female',
}];

const result = data.reduce((c, v) => {
  c[v.sex] = c[v.sex] || [];       //Initiate if key does not exist
  c[v.sex].push(v);                //Push the value
  return c;
}, {});

console.log(result);

If you want the keys to be plural, you can just append 's'

const result = data.reduce((c, v) => {
  let k = v.sex + 's';
  c[k] = c[k] || [];           //Initiate if key does not exist
  c[k].push(v);                //Push the value
  return c;
}, {});

edited May 10, 2018 at 10:08

answered May 10, 2018 at 10:02

Eddie

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1 Comment

Eddie Over a year ago

Happy to help :)

A G · Accepted Answer · 2018-05-10 10:08:19Z

2

Something simple with plain old js -

const data = [{
    name: 'James',
    sex: 'male',
  }, {
    name: 'Mike',
    sex: 'male',
  }, {
    name: 'Janet',
    sex: 'female',
  }, {
    name: 'Mary',
    sex: 'female',
}];

var result = { males: [], females: []};
data.forEach(function(person){
  person.sex === 'male' ? result.males.push(person) : result.females.push(person);
});

console.log(result);

answered May 10, 2018 at 10:08

A G

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1 Comment

Myles Over a year ago

Thank you, love the simplicity

Nikhil Aggarwal · Accepted Answer · 2018-05-10 10:04:19Z

1

Try following

const data = [{name:'James',sex:'male',},{name:'Mike',sex:'male',},{name:'Janet',sex:'female',},{name:'Mary',sex:'female',}];

var result = data.reduce((acc, obj) => {
  acc[obj.sex + "s"] = acc[obj.sex + "s"] || []; 
  acc[obj.sex + "s"].push(obj);
  return acc;
}, {});
console.log(result);

answered May 10, 2018 at 10:04

Nikhil Aggarwal

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Comments

Yosvel Quintero · Accepted Answer · 2018-05-10 10:11:16Z

1

You can do:

const data = [{name: 'James',sex: 'male'}, {name: 'Mike',sex: 'male'}, {name: 'Janet',sex: 'female'}, {name: 'Mary',sex: 'female'}];
const result = data.reduce((a, c) => (a[c.sex + 's'].push(c), a), {males: [], females: []});

console.log(result);

answered May 10, 2018 at 10:11

Yosvel Quintero

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Comments

Luffy · Accepted Answer · 2018-05-10 10:16:44Z

1

Did you answer your question?

const data = [{
    name: 'James',
    sex: 'male',
  }, {
    name: 'Mike',
    sex: 'male',
  }, {
    name: 'Janet',
    sex: 'female',
  }, {
    name: 'Mary',
    sex: 'female',
}];
const sex = {};
data.forEach(item => {
    if (!sex[item.sex]) sex[item.sex] = [];
    sex[item.sex].push(item);
})
console.log(sex);

answered May 10, 2018 at 10:16

Luffy

422 bronze badges

1 Comment

Myles Over a year ago

Yes, thank you - great solution, though I've picked the one using reduce above :)

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