game.js

var buttonColours = ["red", "blue", "green", "yellow"];

var gamePattern = [];
var userClickedPattern = [];

$(".btn").click(function() {

  var userChosenColour = $(this).attr("id");
  userClickedPattern.push(userChosenColour);

  //1. In the same way we played sound in nextSequence() , when a user clicks on a button, the corresponding sound should be played.
  playSound(userChosenColour);

});

function nextSequence() {

  var randomNumber = Math.floor(Math.random() * 4);
  var randomChosenColour = buttonColours[randomNumber];
  gamePattern.push(randomChosenColour);

  $("#" + randomChosenColour).fadeIn(100).fadeOut(100).fadeIn(100);

  //4. Refactor the code in playSound() so that it will work for both playing sound in nextSequence() and when the user clicks a button.
  playSound(randomChosenColour);
}

//2. Create a new function called playSound() that takes a single input parameter called name.
function playSound(name) {

  //3. Take the code we used to play sound in the nextSequence() function and add it to playSound().
  var audio = new Audio("sounds/" + name + ".mp3");
  audio.play();
}