Arrays

Question 1

What is an array?

Answer 1

It’s a data structure that can hold multiple values of different data types.

Arrays are created using square brackets [] and can be populated with values separated by commas.

Each value in an array is assigned an index starting from 0.

Question 2

How do you access elements in an array?

Answer 2

Use a square bracket notation [].

The index of the first element in the array is 0, and the index of the last element is the length of the array minus 1.

For example, myArray[0] will access the first element of the array myArray.

Question 3

What is the length property of an array?

Answer 3

It’s a built-in property of arrays that returns the number of elements in an array.

The length property is automatically updated when elements are added to or removed from the array.

Question 4

What is an array?

Answer 4

an ordered collection of values, identified by an index

Question 5

Can you give an example for destructuring an object or an array?

Answer 5

Destructuring is an expression available in ES6 which enables a succinct and convenient way to extract values of Objects or Arrays and place them into distinct variables.

Array destructuring

// Variable assignment.
const foo = ['one', 'two', 'three'];

const [one, two, three] = foo;
console.log(one); // "one"
console.log(two); // "two"
console.log(three); // "three"

// Swapping variables
let a = 1;
let b = 3;

[a, b] = [b, a];
console.log(a); // 3
console.log(b); // 1

Object destructuring

// Variable assignment.
const o = {p: 42, q: true};
const {p, q} = o;

console.log(p); // 42
console.log(q); // true