button.js

// button
( function( window, factory ) {
  // universal module definition
  if ( typeof module == 'object' && module.exports ) {
    // CommonJS
    module.exports = factory(
        window,
        require('./core'),
        require('fizzy-ui-utils'),
    );
  } else {
    // browser global
    factory(
        window,
        window.InfiniteScroll,
        window.fizzyUIUtils,
    );
  }

}( window, function factory( window, InfiniteScroll, utils ) {

// -------------------------- InfiniteScrollButton -------------------------- //

class InfiniteScrollButton {
  constructor( element, infScroll ) {
    this.element = element;
    this.infScroll = infScroll;
    // events
    this.clickHandler = this.onClick.bind( this );
    this.element.addEventListener( 'click', this.clickHandler );
    infScroll.on( 'request', this.disable.bind( this ) );
    infScroll.on( 'load', this.enable.bind( this ) );
    infScroll.on( 'error', this.hide.bind( this ) );
    infScroll.on( 'last', this.hide.bind( this ) );
  }

  onClick( event ) {
    event.preventDefault();
    this.infScroll.loadNextPage();
  }

  enable() {
    this.element.removeAttribute('disabled');
  }

  disable() {
    this.element.disabled = 'disabled';
  }

  hide() {
    this.element.style.display = 'none';
  }

  destroy() {
    this.element.removeEventListener( 'click', this.clickHandler );
  }

}

// -------------------------- InfiniteScroll methods -------------------------- //

// InfiniteScroll.defaults.button = null;

InfiniteScroll.create.button = function() {
  let buttonElem = utils.getQueryElement( this.options.button );
  if ( buttonElem ) {
    this.button = new InfiniteScrollButton( buttonElem, this );
  }
};

InfiniteScroll.destroy.button = function() {
  if ( this.button ) this.button.destroy();
};

// --------------------------  -------------------------- //

InfiniteScroll.Button = InfiniteScrollButton;

return InfiniteScroll;

} ) );