how to create a key object and value in an array using reduce()

Question

I have an array of objects, and I need to return an object where its key is the type of pet and its value is an array with the names of the pets. but I can't create the array of the names.

let pets=[
    {name:'kity', edad:10,type:'cat'},
    {name:'saske', edad:10,type:'dog'},
    {name:'naruto', edad:10,type:'dog'},
    {name:'goku', edad:10,type:'cat'},
    {name:'flofy', edad:10,type:'dog'},
    {name:'flufin', edad:10,type:'cat'},
    {name:'honey', edad:10,type:'bird'},
    {name:'silvestre', edad:10,type:'cat'},
    {name:'taz', edad:10,type:'dog'},
    {name:'piolin', edad:10,type:'bird'},
    {name:'gogeta', edad:10,type:'dog'},
]

const reduced = pets.reduce((acc, {name,type}) => ({
        ...acc, [`Type${type}`]: acc[...name]
        }), {});

expected

reduce ={
            Typecat:['kity','goku','flufin','silvestre'],
            Typedog:['saske','naruto','flofy','taz','gogeta'],
            Typebird:['honey','piolin']
        }

Does this answer your question? Group array items using object — Heretic Monkey
– Heretic Monkey, Commented Feb 1, 2022 at 15:06

Ankit Agarwal · Accepted Answer · 2022-02-01 15:06:39Z

1

You can do this:

let pets=[
  {name:'kity', edad:10,type:'cat'},
  {name:'saske', edad:10,type:'dog'},
  {name:'naruto', edad:10,type:'dog'},
  {name:'goku', edad:10,type:'cat'},
  {name:'flofy', edad:10,type:''},
  {name:'flufin', edad:10,type:'cat'},
  {name:'honey', edad:10,type:'bird'},
  {name:'silvestre', edad:10,type:'cat'},
  {name:'taz', edad:10,type:'dog'},
  {name:'piolin', edad:10,type:'bird'},
  {name:'gogeta', edad:10,type:'dog'},
];

const result = pets.reduce((acc, item) => {
  if(acc[`Type${item.type}`]) {
    acc[`Type${item.type}`].push(item.name);
  } else {
    acc[`Type${item.type}`] = [item.name];
  }
  return acc;
}, {});

console.log(result);

answered Feb 1, 2022 at 15:06

Ankit Agarwal

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4 Comments

Heretic Monkey Over a year ago

This question has been asked and answered many times; we don't need more answers to the same question.

Ankit Agarwal Over a year ago

@HereticMonkey appreciate that

Víctor Eduardo Duque Rosales Over a year ago

thanks this question has not been asked by reduce()

Heretic Monkey Over a year ago

It's been solved by reduce many time @Victor.

I am L · Accepted Answer · 2022-02-01 15:09:10Z

0

What you can do is:

const result = pets.reduce((acc, item) => {
  const values = acc[item.type] ? acc[item.type].concat(item.name) : [item.name]
  
  return {
    ...acc,
    [item.type]: values
  }
}, {});

answered Feb 1, 2022 at 15:09

I am L

4,6806 gold badges38 silver badges55 bronze badges

2 Comments

Heretic Monkey Over a year ago

With the explanation, "What you can do is", which is not useful to anyone.

I am L Over a year ago

the code is pretty much self explanatory if you know how to use reduce. -_-

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