runGame.js

;(function(exports) {
    // Playing the game
    function difficulty(table) {
        return function(event) {
            var buttonID = event.currentTarget.getAttribute('id');
            if (buttonID === 'hard') {
                table.difficulty = 15;
            } else if (buttonID === 'medium') {
                table.difficulty = 30;
            } else {
                table.difficulty = 45;
            }
            console.log('difficulty', table.difficulty);
        }
    }

    function startGame(table) {
        return function() {
            var tableNode, difficulty, newTable;
            if (table.difficulty === null) {
                alert('Please choose a difficulty.');
                return false;
            }
            if ((tableNode = document.getElementById('table'))) {
                console.log('table has been previously created', table.difficulty);
                difficulty = table.difficulty;
                window.clearInterval(computerInterval);
            }
            newTable = new Table(21);
            newTable.difficulty = table.difficulty || difficulty;
            exports.DomManipulation.newGame(newTable, newTable.difficulty);
        }
    }

    function addDifficultyClicks(table) {
        var buttons = document.getElementsByClassName('difficulty');
        for (var i = 0; i < buttons.length; i++) {
            buttons[i].addEventListener('click', difficulty(table));
        }
        var start = document.getElementById('startgame');
        start.addEventListener('click', startGame(table));
    }

    var table = new Table(21);
    addDifficultyClicks(table);
})(this);