To declare an empty two-dimensional array in JavaScript, we can create an empty array with the Array constructor.
Then we call map on that array with a callback that returns an array with the Array constructor to create the nested arrays.
For instance, we can write:
const nested = [...Array(3)].map(x => Array(5).fill(0))
console.log(nested)
We call Array with 3 to create an array with length 3.
Then we spread that into a new array to create a copy of it.
Next, we call map on the copied array with a callback that returns an array with length with all values in it set to 0 with Array(5).fill(0) .
As a result, nested is a two-dimensional array with length 3, with each nested array with length 5 and all values inside it set to 0.
If we want the nested arrays to be empty, we can omit the fill call.
