Creating [1, 2, 3, 4, 5, 6] in JavaScript

This document outlines various methods to produce the array [1, 2, 3, 4, 5, 6] in JavaScript, including combining arrays, generating sequences, and literal declarations.

Array literal

[1, 2, 3, 4, 5, 6];

Array.of

Array.of(1, 2, 3, 4, 5, 6);

Flat with nested arrays

[[1, 2], [3, 4], [5, 6]].flat();

Array.concat (combining arrays)

var array1 = [1, 2, 3];
var array2 = [4, 5, 6];
array1.concat(array2);

Spread operator (combining arrays)

var array1 = [1, 2, 3];
var array2 = [4, 5, 6];
[...array1, ...array2];

Array.push with spread (modifying array)

var array1 = [1, 2, 3];
var array2 = [4, 5, 6];
array1.push(...array2);

Array.from with mapping

Array.from({ length: 6 }, (_, i) => i + 1);

Array.keys with spread and map

[...Array(6).keys()].map(i => i + 1);

Array.fill and map

Array(6).fill().map((_, i) => i + 1);

Apply with map

Array.apply(null, new Array(6)).map((_, index) => index + 1)

Array.fill and reduce

Array(6).fill().reduce((acc, _, i) => [...acc, i + 1], []);

Object.keys with mapping

Object.keys(Array(6).fill()).map(n => Number(n) + 1);

String split

'123456'.split('').map(Number);

For loop

var array = [];
for (let i = 1; i <= 6; i++) {
  array.push(i);
}

While loop

var array = [];
let i = 1;
while (i <= 6) {
  array.push(i++);
}

Recursive function

function createRange(start, end, arr = []) {
  if (start > end) return arr;
  return createRange(start + 1, end, [...arr, start]);
}
createRange(1, 6);

Generator function

function* range(start, end) {
  for (let i = start; i <= end; i++) {
    yield i;
  }
}
[...range(1, 6)];

eval

eval('[' + Array.from({length: 6}, (_, i) => i + 1).join(',') + ']');

everget/js-1-2-3-4-5-6.md