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

February 1, 2022

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']
        }

>Solution :

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);