Use the fill method to fill an array with values.
Example:
const a = new Array(3).fill(-1);
// Result: a = [-1, -1, -1]
The fill method can be called on an existing array as well to fill it with the defined value.
Creating a two-dimensional array with an initial value (e.g. 3x5 matrix):
const a = [...Array(3)].map(e => Array(5).fill(0))