https://www.lowyat.net/wp-content/plugins/jnews-auto-load-post/assets/js/jquery.autoload-queue.js

1/**
2 * JNews Auto-Load Next Post — queue driver
3 *
4 * Patches the base jautoload plugin so it navigates a pre-built, server-side
5 * ordered sequence (tag → category → sequence) instead of following a lazy
6 * per-post data-prev chain.
7 *
8 * Activation: the PHP side stamps data-autoload-queue (a JSON array of
9 * { id, url } objects) onto the first .post-autoload element only when the
10 * "tag_category" mode is active and the request is NOT an autoload AJAX call.
11 * This script is only enqueued when that mode is selected, so there is zero
12 * overhead for sites using any other mode.
13 *
14 * How the index works:
15 *   - Initially 1 post (.post-autoload) is in the DOM  → we want queue[0]
16 *   - After the 1st AJAX post loads, count = 2          → we want queue[1]
17 *   - After the 2nd AJAX post loads, count = 3          → we want queue[2]
18 *   index = $(content_class).length - 1
19 *
20 * This is stateless (no shift/pop) and naturally self-corrects even if
21 * change_url fires multiple times for the same scroll event, because the
22 * existing check_loaded() guard in auto_load_prev_post prevents double-loading.
23 */
24( function ( $ ) {
25	'use strict';
26
27	var Constructor = $.fn.jautoload && $.fn.jautoload.Constructor;
28	if ( ! Constructor ) { return; }
29
30	var _init             = Constructor.prototype.init;
31	var _get_previous_url = Constructor.prototype.get_previous_url;
32
33	/**
34	 * Override init — read the pre-built queue from the first post's attribute
35	 * and store it on the instance before waypoints are initialised.
36	 */
37	Constructor.prototype.init = function () {
38		var queueData         = $( this.content_class ).first().data( 'autoload-queue' );
39		this.autoload_queue   = Array.isArray( queueData ) ? queueData : null;
40		_init.call( this );
41	};
42
43	/**
44	 * Override get_previous_url — return the next URL from the pre-built queue
45	 * when one is present, otherwise fall through to the original behaviour.
46	 */
47	Constructor.prototype.get_previous_url = function ( e, n ) {
48		if ( this.autoload_queue ) {
49			// Number of .post-autoload elements currently in the DOM tells us
50			// exactly which queue entry to serve next.
51			var loaded    = $( this.content_class ).length;
52			var nextIndex = loaded - 1;
53
54			if ( nextIndex < this.autoload_queue.length ) {
55				return this.autoload_queue[ nextIndex ].url;
56			}
57
58			return null; // queue exhausted — stop loading
59		}
60
61		return _get_previous_url.call( this, e, n );
62	};
63
64}( jQuery ) );