Arrays

An array is a data structure that contains any number of items (or elements). In JavaScript, array elements can be of any data type.

Create an empty array:

const arr = []

Elements in the array should be separated by commas.

const satchel = [
  'chair',
  'table',
  'candle',
  'map',
  'magnifying glass',
  'rupees',
  'Quick Eze',
  'boomerang'
]

const squares = [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

Accessing Elements

Each element in the array has a numbered index. The first element has an index of 0.

Access elements by putting the index number in square brackets.

const satchel = [
  'chair',
  'table',
  'candle',
  'map',
  'magnifying glass',
  'rupees',
  'Quick Eze',
  'boomerang'
]

console.log(satchel[0]) // => 'chair'
console.log(satchel[1]) // => 'table'

Getting the Number of Elements in an Array

We can use the .length property to find out the number of elements in an array

const satchel = [
  'chair',
  'table',
  'candle',
  'map',
  'magnifying glass',
  'rupees',
  'Quick Eze',
  'boomerang'
]

console.log(satchel.length) // => 8

Changing Elements

• To change an element in an array, first access the element, and then assign a new value:

const satchel = [
  'chair',
  'table',
  'candle',
  'map',
  'magnifying glass',
  'rupees',
  'Quick Eze',
  'boomerang'
]

satchel[2] = 'glowing orb'

console.log(satchel)

NOTE: const only prevents reassignment, the value can still be mutated.

Iterate over an array

Let's use a for..of loop to iterate over the array and print each element out.

for (let item of satchel) {
  console.log(`A nimble rogue is trying to steal my ${item}!!!1`)
}