Skip to Content


Attempt to predict the next pageview for caching/prefetching.

JavaScript February 7, 2021




This function does not accept any parameters. Is this incorrect?

Additional Notes

If a service worker is being used (and Cache API is available), the resource will be fetched and added to the cache. Otherwise, it will attempt to prefetch with a resource hint instead.

It also does not run when offline.

Note: This only enables event listeners! To add to the cache, see nebulaAddToCache() ornebulaPrefetch().

Was this page helpful? Yes No

    A feedback message is required to submit this form.

    Please check that you have entered a valid email address.

    Enter your email address if you would like a response.

    Thank you for your feedback!

    Source File

    Located in /assets/js/modules/optimization.js on line 357.

    No Hooks

    This function does not have any filters or actions available. Request one?
    nebula.predictiveCacheListeners = async function(){
        //If Save Data is supported and Save Data is requested do not bother with predictive listeners
        if ( navigator.connection?.saveData ){
            return false;
        //Any post listing page
        if ( jQuery('.first-post .entry-title a').length ){
            nebula.prefetch(jQuery('.first-post .entry-title a').attr('href'));
        //Internal link hovers
        let predictiveHoverTimeout;
        jQuery('a').on('mouseenter', function(){
            let $oThis = jQuery(this);
            let url = $oThis.attr('href');
            if ( url && !predictiveHoverTimeout ){
                predictiveHoverTimeout = window.setTimeout(function(){
                    predictiveHoverTimeout = null; //Reset the timer
                    nebula.prefetch(url); //Attempt to prefetch
                }, 250);
        }).on('mouseleave', function(){
            if ( predictiveHoverTimeout ){
                predictiveHoverTimeout = null;
        //Once idle, prefetch the top-level nav items and buttons
        //Disabled to reduce the broad background loading. The above hover prefetch is more focused.
    //     if ( typeof window.requestIdleCallback === 'function' ){ //Waiting for Safari to support requestIdleCallback
    //         //Prefetch certain elements on window idle
    //         window.requestIdleCallback(function(){
    //             //Top-level primary nav links
    //             jQuery('ul#menu-primary > > a').each(function(){
    //                 nebula.prefetch(jQuery(this).attr('href'), false, jQuery(this));
    //             });
    //             //First 5 buttons
    //             jQuery('a.btn, a.wp-block-button__link').slice(0, 4).each(function(){
    //                 nebula.prefetch(jQuery(this).attr('href'), false, jQuery(this));
    //             });
    //         });
    //     }


    To override or disable this JavaScript function, simply redeclare it with the exact same function name. Remember: Some functionality is conditionally loaded via dynamic imports, so if your function is not overriding properly, try listening for a DOM event (described below).


    For non-module import functions:

    nebula.predictiveCacheListeners = function(){
        //Write your own code here, leave it blank, or return false.

    For dynamically imported module function overrides:

    jQuery(window).on('load', function(){
        nebula.predictiveCacheListeners = function(){
            //Write your own code here, leave it blank, or return false.

    Custom Nebula DOM events do also exist, so you could also try the following if the Window Load listener does not work:

    jQuery(document).on('nebula_module_loaded', function(module){
        //Note that the module variable is also available to know which module specifically was imported
        if ( typeof nebula.predictiveCacheListeners === 'function' ){
            nebula.predictiveCacheListeners = function(){
                //Write your own code here, leave it blank, or return false.