Basic Data Structures: Modify an Array Stored in an ObjectPassed

JavaScript
1

Tell us what’s happening:
please i tried to use concat() method.It seemed to work but FCC did not pass it. Pls can anyone tell the why?

Your code so far


let user = {
name: 'Kenneth',
age: 28,
data: {
  username: 'kennethCodesAllDay',
  joinDate: 'March 26, 2016',
  organization: 'freeCodeCamp',
  friends: [
    'Sam',
    'Kira',
    'Tomo'
  ],
  location: {
    city: 'San Francisco',
    state: 'CA',
    country: 'USA'
  }
}
};

function addFriend(userObj, friend) {
// change code below this line
return userObj.data.friends.concat(friend);
// change code above this line
}

console.log(addFriend(user, 'Pete'));

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 6.3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.87 Safari/537.36.

Challenge: Modify an Array Stored in an Object

Link to the challenge:
https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/basic-data-structures/modify-an-array-stored-in-an-object

2

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.

You are returning a new array with all the correct values, but you haven’t actually altered the friends array nested in userObj.

2 Likes
3

As suggested by @colinthornton concate used to merge two or more arrays and will return a new array.

you can try using push array method for adding ‘friend’ to friends array.

userObj.data.friends.push(friend);
return userObj.data.friends;

2 Likes
4

Thanks @colinthornton for the helpful explanation! Glad to have you there! And more power to your elbow.

5

I cannot appreciate your help enough @natasha016. My journey into the programming world is made really real! thanks.

6

One of the big pushes for ES6 is “maintain data immutability!” What that means is, rather than changing the existing array, we should create a new one and simply point the userObj.data.friends at that. An easy way, using ES6 operators? The spread operator will work here:

userObj.data.friends = [...userObj.data.friends, friend] 
// create a new array, spread the existing array in that, and add the new record to the end.
return userObj.data.friends;

Just suggesting, there’s always more than one way to skin a cat. :wink:

1 Like
7