Implement and test displayCountDown() method per comments. (JAVASCRIPT)  displayCountDown: function() { // TODO [F]: Update countdown span element with current countdown value  // Hint: Get a reference to count down span and set the span textContent property with the counter }, startCountDownTimer: function(start) { this._startCount = start; this._counter = this._startCount; this.displayCountDown(); this._intervalID = setInterval(this.countDown.bind(this), 1000); },