ES6 Array Concatenation

1// With Spread
2const arr1 = [1,2,3]
3const arr2 = [4,5,6]
4const merged = [...arr1, ...arr2]
5
6// With Concat and Spread
7const merged = [].concat(...arr1,...arr2);
8
9// With Reduce and Spread
10const arr1 = [1, 2, 3];
11const arr2 = [4, 5, 6];
12function concat(...args) {
13  return args.reduce((acc, val) => [...acc, ...val]);
14}
15concat(arr1, arr2, [7, 8, 9]);
16