How to create an array of numbers from 1 to N

Short answer

Array.from() with a length creates an array and fills it using the index:

const numbers = Array.from({ length: 5 }, (_, i) => i + 1);
 
console.log(numbers.join(', '));

Output:

1, 2, 3, 4, 5

With a step

A function for a range from start to end with any step:

const range = (start, end, step = 1) =>
  Array.from({ length: Math.floor((end - start) / step) + 1 }, (_, i) => start + i * step);
 
console.log(range(0, 20, 5).join(', '));
console.log(range(10, 15).join(', '));

Output:

0, 5, 10, 15, 20
10, 11, 12, 13, 14, 15

The same value

fill() fills an array with one value:

console.log(new Array(3).fill(0).join(', '));

Output:

0, 0, 0

Common mistake

fill() with an object puts the same object into every cell. Use Array.from() with a function to get separate objects:

const shared = new Array(2).fill({ count: 0 });
shared[0].count = 5;
 
const separate = Array.from({ length: 2 }, () => ({ count: 0 }));
separate[0].count = 5;
 
console.log(shared[1].count, separate[1].count);

Output:

5 0

Thanks for reading!

Short answer

With a step

The same value

Common mistake

Functions used in this recipe

Thanks for reading!