https://www.unn.edu.ng/wp-content/plugins/the-preloader/js/thePreloader.js?ver=2.0.2

1/**
2 * ThePreloader.js
3 * A lightweight preloader plugin.
4 * 
5 * @author    Alobaidi
6 * @version   1.0.0
7 */
8
9class ThePreloader {
10    constructor(options = {}) {
11        this.options = {
12            preloaderElement: typeof options.preloaderElement === 'string' && options.preloaderElement.trim() 
13                ? options.preloaderElement.toLowerCase().trim() 
14                : 'the-preloader-element'
15        };
16
17        this.preloader = document.getElementById(this.options.preloaderElement);
18
19        this.init = this.init.bind(this);
20        this.hidePreloader = this.hidePreloader.bind(this);
21    }
22
23    fadeOut(element, duration) {
24        return new Promise(resolve => {
25            element.style.transition = `opacity ${duration}s ease-in-out`;
26            element.style.opacity = '0';
27            
28            setTimeout(() => {
29                element.style.display = 'none';
30                resolve();
31            }, duration * 1000 + 50);
32        });
33    }
34
35    async hidePreloader() {
36        await new Promise(resolve => 
37            setTimeout(resolve, 500)
38        );
39
40        await this.fadeOut(this.preloader, 0.5);
41        
42        setTimeout(() => {
43            this.preloader.remove();
44        }, 50);
45    }
46
47    init() {
48        if ( !this.preloader ) {
49            console.log('ThePreloader.js: Preloader element does not exist.');
50            return;
51        }
52
53        this.hidePreloader();
54    }
55}
56
57document.addEventListener('DOMContentLoaded', function() {
58
59    window.addEventListener('load', () => {
60        const the_Preloader = new ThePreloader({
61            preloaderElement: 'the-preloader-element'
62        });
63        the_Preloader.init();
64    });
65
66});