in javascript how would I create an empty array of a given size
Psuedo code:
X = 3; createarray(myarray, X, ""); output:
myarray = ["","",""] 8 Answers
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]
var arr = new Array(5); console.log(arr.length) // 5 We use Array.from({length: 500}) since 2017.
As of ES5 (when this answer was given):
If you want an empty array of undefined elements, you could simply do
var whatever = new Array(5); this would give you
[undefined, undefined, undefined, undefined, undefined] In newer versions, this now gives
[empty × 5] See this other question on the difference between empty and undefined.
If you wanted it to be filled with empty strings, you could do
whatever.fill(''); which would give you
["", "", "", "", ""] And if you want to do it in one line:
var whatever = Array(5).fill(''); Try using while loop, Array.prototype.push()
var myArray = [], X = 3; while (myArray.length < X) { myArray.push("") } Alternatively, using Array.prototype.fill()
var myArray = Array(3).fill(""); In 2018 and thenceforth we shall use [...Array(500)] to that end.
If you want to create anonymous array with some values so you can use this syntax.
var arr = new Array(50).fill().map((d,i)=>++i) console.log(arr)You can use both javascript methods repeat() and split() together.
" ".repeat(10).split(" ") This code will create an array that has 10 item and each item is empty string.
const items = " ".repeat(10).split(" ") document.getElementById("context").innerHTML = items.map((item, index) => index) console.log("items: ", items)<pre> </pre>
