Javascript Array and Object

Given a number of elements that need to stay in order, would you use an Object or an Array?

• Object

• Array

Given a collection of artists and lists of their songs, would you store the artist-song-list pairs in an Object or an Array?

• Object

• Array

All the elements in an array must be of the same type.

• True

• False

All keys in an object are strings.

• True

• False

Answer explanation

https://www.becomebetterprogrammer.com/can-javasscript-object-keys-be-numbers-or-non-string-values

What happens to the array in the following code snippet?

const dogs = ["Fido", "Odie", "Oscar"];

dogs.length;

dogs.length = 1;

dogs; // What will the array contain here?

• Nothing

• The array becomes just ["Oscar"]

• The array becomes just ["Fido"]

• The array becomes just ["Odie", "Oscar"]

What are the keys in the object after running the code below?

• ['Prince', 'The Beatles', 'Joni Mitchell', 'Justin Bieber', 'Daft Punk']

• ['Prince', 'The Beatles', 'Joni Mitchell', 'Justin Bieber']

• ['Prince', 'The Beatles', 'Joni Mitchell']

• ['Prince', 'The Beatles', 'Joni Mitchell', 'Daft Punk']

If we run artistsAndSongs['Daft Punk'].push("Around the World") after running the code below, what is the value of the object?

• 
• 
• 
• 

What is the result of the following code in a browser that supports the spread operator?

const oneTwoThree = [1, 2, 3];

const sevenEightNine = [7, 8, 9];

[4, 5, 6, ...oneTwoThree, ...sevenEightNine];

• [4, 5, 6, 7, 8, 9, 1, 2, 3]

• [4, 5, 6, 1, 2, 3, 7, 8, 9]

• [1, 2, 3, 4, 5, 6, 7, 8, 9]

• Error

Given the array const letters = ["alpha", "gamma", "delta"], which operation(s) return the array ["alpha", "beta", "gamma", "delta"]?

• letters.push("beta")

• letters.unshift('beta')

• [...letters.slice(0, 1), 'beta', ...letters.slice(1)]

• letters.splice(1, 1, 'beta')

• letters.splice(1, 0, 'beta')