User:Jdlrobson/scripts/backtotop.js

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Documentation for this user script can be added at User:Jdlrobson/scripts/backtotop. This user script seems to have an accompanying .css page at User:Jdlrobson/scripts/backtotop.css.

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mw.loader.load( '/w/index.php?title=User:Jdlrobson/scripts/backtotop.css&action=raw&ctype=text/css', 'text/css' );

var backtotop,
    // eslint-disable-next-line no-restricted-properties
    M = mw.mobileFrontend,
    mobile = M.require( 'mobile.startup' ),
    View = mobile.View,
    browser = mobile.Browser.getSingleton(),
    eventBus = mobile.eventBusSingleton;

/**
    * Displays a little arrow at the bottom right of the viewport.
    * @class BackToTopOverlay
    * @extends View
    * @param {Object} props
    */
function BackToTopOverlay( props ) {
    View.call( this,
        $.extend( {}, props, {
            className: 'backtotop',
            events: { click: 'onBackToTopClick' }
        } )
    );
}

OO.inheritClass( BackToTopOverlay, View );

BackToTopOverlay.prototype.template = mw.template.get( 'skins.minerva.options', 'BackToTopOverlay.mustache' );

/**
    * Show the back to top element, if it's not visible already.
    * @memberof BackToTopOverlay
    * @instance
    */
BackToTopOverlay.prototype.show = function () {
    this.$el.css( 'visibility', 'visible' ).addClass( 'visible' );
};

/**
    * Hide the back to top element, if it's visible.
    * @memberof BackToTopOverlay
    * @instance
    */
BackToTopOverlay.prototype.hide = function () {
    this.$el.removeClass( 'visible' );
};

/**
    * Handles the click on the "Back to top" element and scrolls back
    * to the top smoothly.
    * @memberof BackToTopOverlay
    * @instance
    */
BackToTopOverlay.prototype.onBackToTopClick = function () {
    // eslint-disable-next-line no-jquery/no-global-selector
    $( 'html, body' ).animate( { scrollTop: 0 }, 400 );
};



backtotop = new BackToTopOverlay();
// initialize the back to top element
backtotop.appendTo( 'body' );

eventBus.on( 'scroll', function () {
    if ( $( window ).height() - $( window ).scrollTop() <= 0 ) {
        backtotop.show();
    } else {
        backtotop.hide();
    }
} );