Javascript, extracting out a single element from an array into an object with the new array formed from the matching sets

Question

Suppose I have a series of arrays like this:

[{title: 'foo', data: 'something here'}, 
 {title: 'foo', data: 'something else here'}, 
 {title: 'bar', data: 'something else again'}
]

What would be nice is if I could transform them into a series of objects grouped by title as the key.

So the transformation would look something like this:

{
    'foo': {data: ['something else', 'something else here']}
    'bar': {data: ['something else again']}
}

How would I go about that in a somewhat elegant manner?

Wyatt Arent · Accepted Answer · 2018-04-19 23:34:13Z

3

What you're looking for is the reduce function.

let myArray = [
  {title: 'foo', data: 'something here'}, 
  {title: 'foo', data: 'something else here'}, 
  {title: 'bar', data: 'something else again'}
];


myArray = myArray.reduce((obj, value) => {

  // Check to see if the "Title" exists in the object
  if (!obj[value.title]) {

    // If not, create it
    // and initialize "data" as an empty array
    obj[value.title] = {
      data: []
    };
  }

  // Push data to the data array in our object
  obj[value.title].data.push(value.data);

  return obj;

}, {});

answered Apr 19, 2018 at 23:34

Wyatt Arent

5883 silver badges9 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

sumit · Accepted Answer · 2018-04-19 23:44:05Z

1

You can apply reduce,filter and map

let arr=[{title: 'foo', data: 'something here'}, 
 {title: 'foo', data: 'something else here'}, 
 {title: 'bar', data: 'something else again'}
]
const convert_to_object = (myarray) =>
   myarray.reduce((o, i) => {
     o[i.title] = {data:myarray.filter(m=>m.title==i.title).map(m=>m.data)}
     return o
   }, {})
const someobj = convert_to_object(arr)
console.log(someobj)

answered Apr 19, 2018 at 23:44

sumit

15.5k14 gold badges75 silver badges113 bronze badges

2 Comments

Michael Ryan Soileau Over a year ago

Your JavaScript kung-fu is strong my friend, but I'm marking the other person correct because he doesn't have your high rep. :) You still get the upvote.

Wyatt Arent Over a year ago

FYI this solution is O(n^2) rather than the solution I provided above which is O(n). Would advise actually not using nested loops like this

Collectives™ on Stack Overflow

Javascript, extracting out a single element from an array into an object with the new array formed from the matching sets

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related