Display a loading bar before the entire page is loaded

I would like to display a loading bar before the entire page is loaded. For now, I'm just using a small delay:

$(document).ready(function(){
	$('#page').fadeIn(2000);
});

The page already uses jQuery.

Note: I have tried this, but it didn't work for me: loading bar while the script runs

I also tried other solutions. In most cases, the page loads as usual, or the page won't load/display at all.

Use a div #overlay with your loading info / .gif that will cover all your page:

<div id="overlay">
     <img src="loading.gif" alt="Loading" />
     Loading...
</div>

jQuery:

$(window).load(function(){
   // PAGE IS FULLY LOADED  
   // FADE OUT YOUR OVERLAYING DIV
   $('#overlay').fadeOut();
});

---

Here's an example with a Loading bar:

jsBin demo

;(function(){
  function id(v){ return document.getElementById(v); }
  function loadbar() {
    var ovrl = id("overlay"),
        prog = id("progress"),
        stat = id("progstat"),
        img = document.images,
        c = 0,
        tot = img.length;
    if(tot == 0) return doneLoading();

    function imgLoaded(){
      c += 1;
      var perc = ((100/tot*c) << 0) +"%";
      prog.style.width = perc;
      stat.innerHTML = "Loading "+ perc;
      if(c===tot) return doneLoading();
    }
    function doneLoading(){
      ovrl.style.opacity = 0;
      setTimeout(function(){ 
        ovrl.style.display = "none";
      }, 1200);
    }
    for(var i=0; i<tot; i++) {
      var tImg     = new Image();
      tImg.onload  = imgLoaded;
      tImg.onerror = imgLoaded;
      tImg.src     = img[i].src;
    }    
  }
  document.addEventListener('DOMContentLoaded', loadbar, false);
}());

*{margin:0;}
body{ font: 200 16px/1 sans-serif; }
img{ width:32.2%; }

#overlay{
  position:fixed;
  z-index:99999;
  top:0;
  left:0;
  bottom:0;
  right:0;
  background:rgba(0,0,0,0.9);
  transition: 1s 0.4s;
}
#progress{
  height:1px;
  background:#fff;
  position:absolute;
  width:0;                /* will be increased by JS */
  top:50%;
}
#progstat{
  font-size:0.7em;
  letter-spacing: 3px;
  position:absolute;
  top:50%;
  margin-top:-40px;
  width:100%;
  text-align:center;
  color:#fff;
}

<div id="overlay">
  <div id="progstat"></div>
  <div id="progress"></div>
</div>

<div id="container">
  <img src="http://placehold.it/3000x3000/cf5">
</div>

HTML

<div class="preload">
<img src="http://i.imgur.com/KUJoe.gif">
</div>

<div class="content">
I would like to display a loading bar before the entire page is loaded. 
</div>

JAVASCRIPT

$(function() {
    $(".preload").fadeOut(2000, function() {
        $(".content").fadeIn(1000);        
    });
});​

CSS

.content {display:none;}
.preload { 
    width:100px;
    height: 100px;
    position: fixed;
    top: 50%;
    left: 50%;
}
​

DEMO

Whenever you try to load any data in this window this gif will load.

HTML

Make a Div

<div class="loader"></div>

CSS .

.loader {
    position: fixed;
    left: 0px;
    top: 0px;
    width: 100%;
    height: 100%;
    z-index: 9999;
    background: url('https://lkp.dispendik.surabaya.go.id/assets/loading.gif') 50% 50% no-repeat rgb(249,249,249);

jQuery

$(window).load(function() {
        $(".loader").fadeOut("slow");
});
<script src="https://code.jquery.com/jquery-1.9.1.min.js"></script>

I've recently made a page loader in VanillaJS for a project, just wanted to share it as, all the other answers, are jQuery based. It's a plug and play, one-liner.

let settings={backgroundColor:"#2774ab",filterBrightness:2,timeOnScreen:100},u=document.querySelector("*"),s=document.createElement("style"),a=document.createElement("div"),m="http://www.w3.org/2000/svg",g=document.createElementNS(m,"svg"),c=document.createElementNS(m,"circle");document.head.appendChild(s),s.innerHTML="@keyframes swell{to{transform:rotate(360deg)}}",a.setAttribute("style","background-color:"+settings.backgroundColor+";color:"+settings.backgroundColor+";display:flex;align-items:center;justify-content:center;position:fixed;top:0;height:100vh;width:100vw;z-index:2147483647"),document.body.prepend(a),g.setAttribute("style","height:50px;filter:brightness("+settings.filterBrightness+");animation:.3s swell infinite linear"),g.setAttribute("viewBox","0 0 100 100"),a.prepend(g),c.setAttribute("cx","50"),c.setAttribute("cy","50"),c.setAttribute("r","35"),c.setAttribute("fill","none"),c.setAttribute("stroke","currentColor"),c.setAttribute("stroke-dasharray","165 57"),c.setAttribute("stroke-width","10"),g.prepend(c),u.style.pointerEvents="none",u.style.userSelect="none",u.style.cursor="wait",window.onload=(()=>{setTimeout(()=>{u.style.pointerEvents="",u.style.userSelect="",u.style.cursor="",a.remove()},settings.timeOnScreen)});

Fundamentals

• Generate a <script> element appended to the <head> element, containing any required styling.
• Generate a <div> element, acting as overlay, prepended to the <body> element.
• Generate a <svg> element, acting as loader, prepended to the previously generated <div> element.
• On window.onload self generated elements are automatically removed.

> ### The latest version is available on my GitHub.

Demo

https://i.ibb.co/L68sYxD/Vanilla-js-pages-transitions-loader-ressource-1.gif"></img>	https://i.ibb.co/ZH4PXWZ/vanilla-js-pages-transitions-loader-ressource-2.gif"></img>	https://i.ibb.co/J7y9BYy/vanilla-js-pages-transitions-loader-ressource-3.gif"></img>

Settings

let settings = {
    backgroundColor: "#2774ab",
    filterBrightness: 2,
    timeOnScreen: 100
}, //...

Option	Description
backgroundColor	Refer to MDN Web Docs color for acceptable values. The background-color CSS property sets the background color of an element. Default to Wordpress deep blue accent #2774ab
filterBrightness	number or percentage. The brightness of the svg loader element (brightness() CSS function). A value under 100% darkens the loader, while a value over 100% brightens it. The lacuna value for interpolation is 1. Default to 2.
timeOnScreen	Positive integer. The time on screen is appended to the page loading time. Default to 100 milliseconds.

Semantic UI might also help, with just simple one liner to show and to hide the loading icon.

Eg: <div class="ui active centered inline loader"></div>

Source: https://semantic-ui.com/elements/loader.html

Found a code sample: https://codepen.io/fujiyamayuta/pen/JBxxJO

Although, there is a small typo in the JS file of the above code sample, corrected is shown below:

// ** Loader ON
$('#dimmer').dimmer('show');

// ** Loader OFF
// $('#dimmer').dimmer('hide');