code: 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);
  	  }
docs: Check if media is loading