For people using ES2015 (ES6)
You can now use the Spread Syntax to concatenate arrays:
const arr1 = [0, 1, 2],
arr2 = [3, 4, 5];
const result1 = [...arr1, ...arr2]; // -> [0, 1, 2, 3, 4, 5]
// or...
const result2 = [...arr2, ...arr1]; // -> [3, 4, 5, 0, 1, 2]
