Check if media is loading
function checkLoading(event) {
	    var _this4 = this;

	    this.loading = ['stalled', 'waiting'].includes(event.type); // Clear timer

	    clearTimeout(this.timers.loading); // Timer to prevent flicker when seeking

	    this.timers.loading = setTimeout(function () {
	      // Update progress bar loading class state
	      toggleClass(_this4.elements.container, _this4.config.classNames.loading, _this4.loading); // Update controls visibility

	      ui.toggleControls.call(_this4);
	    }, this.loading ? 250 : 0);
	  }