deckOfCards.js

'use strict';
let getDeck = () => {
  let deck = [];
  const numVal = _.range(2, 11).map(String);
  const faceVal = ['J', 'Q', 'K', 'A'];
  const value = numVal.concat(faceVal);
  const suits = ['♠', '♥', '♣', '♦'];
  for (var suit of suits) {
    const cards = value.map(val => val + suit);
    deck.push(cards);
  }

  deck = _.flatten(deck);
  return deck;
};

console.log(getDeck());

// ["2♠","3♠","4♠","5♠","6♠","7♠","8♠","9♠","10♠","J♠","Q♠","K♠","A♠",
//  "2♥","3♥","4♥","5♥","6♥","7♥","8♥","9♥","10♥","J♥","Q♥","K♥","A♥",
//  "2♣","3♣","4♣","5♣","6♣","7♣","8♣","9♣","10♣","J♣","Q♣","K♣","A♣",
//  "2♦","3♦","4♦","5♦","6♦","7♦","8♦","9♦","10♦","J♦","Q♦","K♦","A♦"]