concat method of an array.
let a = [1, 2, 3] let b = [4, 5, 6] a.concat(b) //concat though is not mutative, you have to assign the result let c = a.concat(b) // we have concatenated
Whether or not
Array.prototype.concat is mutative has always been something I get wrong. Some
Array methods are mutative some are not! By using the spread operator, I never get this wrong (it’s not mutative).
let c = [...[1, 2, 3], ...[4, 5, 6]] console.log(c) // [1, 2, 3, 4, 5, 6]