Given a JavaScript array, how do you get just the first X items of it?

Use the built-in slice() method that comes with each array instance:

const arrayToCut = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

const n = 5 //get the first 5 items

const newArray = arrayToCut.slice(0, n)

Note that the original array is not modified in this operation.