Array and Object And When to Use Each Of Them

Where are lot of articles about this exact subject around the web, but, since I feel this doesn't clear anought for me - I feel like write a post about...

Object(Old good javascript object)

Pretty common scenario - when you have list of objects came from API:

const users = [
  {id:'123', name: 'Moshe'},
  {id:'124', name: 'Vasia'},
]

and you need to access one of the objects by its 'id' - you can do it by searching through the array, like this:

const currentUser = users.find(({id}) => id === '123');

But, of course, if you have array with lot of users - it will be much quicker to access some certain user by id - if "users" were stored inside Object with following structure:

const users = {
  '123': {id:'123', name: 'Moshe'},
  '124': {id:'124', name: 'Vasia'},
}
const currentUser = users['123'];

BTW, for optimize your performance you can restructure the users collection from array to object using following code:

let optimizedUsers = users.reduce((acc, user) => {
  return {
    ...acc,
    [user.id]: user  
  };
}, {});
const currenttUser = optimizedUsers['123'];
console.log(currenttUser.name); // will print "Moshe" 

You just saw the scenario with advantage of using Object upon Array