JavaScript — How to create and fill an empty array with a given size?

Solution

const arr = Array(5).fill("");
console.log(arr); //prints out ["","","","",""]
console.log(arr[0]); //prints out ""

1) To create new array which, you cannot iterate over, you can use array constructor:

Array(100) or new Array(100)

2) You can create new array, which can be iterated over like below:

a) All JavaScript versions

• Array.apply: Array.apply(null, Array(100))

b) From ES6 JavaScript version

• Destructuring operator: [...Array(100)]
• Array.prototype.fill Array(100).fill(undefined)
• Array.from Array.from({ length: 100 })

You can map over these arrays like below.

• Array(4).fill(null).map((u, i) => i) [0, 1, 2, 3]
• [...Array(4)].map((u, i) => i) [0, 1, 2, 3]
• Array.apply(null, Array(4)).map((u, i) => i) [0, 1, 2, 3]
• Array.from({ length: 4 }).map((u, i) => i) [0, 1, 2, 3]