javascript create empty array of a given size

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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]

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