Use array spread to add or change an array item

Add an item (push)
const items = [1, 2, 3]
const clone = [
    … items, 
    4,
]
// items [1,2,3]
// clone [1,2,3,4]

Add to the beginning (unshift)
const items = [1, 2, 3]
const clone = [
    4, 
    …items,
]
// items [1, 2, 3]
// clone [4,1,2,3]

Change an item
const items = [1,2,3]
const index = items.indexOf(2)
const clone = [
    …items.slice(0, index)
    77,
    …items.slice(index +1)
]
// items [1,2,3]
// clone [1,77,3]