const a = [1, 2, 3];const b = [4, 5, 6];const c = [7, 8, 9]; const final = [...a, ...b, ...c]; // [1, 2, 3, 4, 5, 6, 7, 8, 9]
`push`
const a = [1, 2, 3];const b = [4, 5, 6]; a.push(...b);a; // [1, 2, 3, 4, 5, 6]