Using es6 spread to concat multiple arrays

Question

We all know you can do:

let arr1 = [1,2,3];
let arr2 = [3,4,5];
let arr3 = [...arr1, ...arr2]; // [1,2,3,3,4,5]

But how do you make this dynami

Answer 1

We can resolve using es6 following way

function mergeTwo(arr1, arr2) {
  let result = [...arr1, ...arr2];
  return result.sort((a,b) => a-b);
}