jaxon-php / jaxon-js

(function(self) {

    "use strict";

    let readyList = [];

    let readyFired = false;

    let readyEventHandlersInstalled = false;

    /**

     * Call this when the document is ready.

     * This function protects itself against being called more than once

     */

    const ready = () => {

        if (readyFired) {

            return;

        }

        // this must be set to true before we start calling callbacks

        readyFired = true;

        // if a callback here happens to add new ready handlers,

        // the jaxon.dom.ready() function will see that it already fired

        // and will schedule the callback to run right after

        // this event loop finishes so all handlers will still execute

        // in order and no new ones will be added to the readyList

        // while we are processing the list

        readyList.forEach(cb => cb.fn.call(window, cb.ctx));

        // allow any closures held by these functions to free

        readyList = [];

    }

    // Was used with the document.attachEvent() function.

    // const readyStateChange = () => document.readyState === "complete" && ready();

    /**

     * This is the one public interface

     * jaxon.dom.ready(fn, context);

     * The context argument is optional - if present, it will be passed as an argument to the callback

     */

    self.ready = function(callback, context) {

        // if ready has already fired, then just schedule the callback

        // to fire asynchronously, but right away

        if (readyFired) {

            setTimeout(function() { callback(context); }, 1);

            return;

        }

        // add the function and context to the list

        readyList.push({ fn: callback, ctx: context });

        // if document already ready to go, schedule the ready function to run

        if (document.readyState === "complete" ||

            (!document.attachEvent && document.readyState === "interactive")) {

            setTimeout(ready, 1);

            return;

        }

        if (!readyEventHandlersInstalled) {

            // first choice is DOMContentLoaded event

            document.addEventListener("DOMContentLoaded", ready, false);

            // backup is window load event

            window.addEventListener("load", ready, false);

            readyEventHandlersInstalled = true;

        }

    }