Array of Arrays flatten with reduce

flatarray.js

const mult = [songs, [{id: 112, name: "Chop Suey", artist: "System of a Down" }]];

var flatMult = mult.reduce(function (acc, currValue) {
  return acc.concat(currValue);
}, []);

// ES6
const flatMult = mult.reduce((acc, currValue) => {
  return acc.concat(currValue);
}, []);

console.log(flatMult); 

// [
//  { id: 1, name: "Curl of the Burl", artist: "Mastodon" },
//  { id: 2, name: "Oblivion", artist: "Mastodon" },
//  { id: 3, name: "Flying Whales", artist: "Gojira" },
//  { id: 4, name: "L'Enfant Sauvage", artist: "Gojira" },
//  { id: 112, name: "Chop Suey", artist: "System of a Down" },
// ]