How to Show Page Loading Div Until the Page Has Finished Loading

Loading div page that shows until the page has loaded fully PLUS two seconds

<!DOCTYPE html>

<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8" />
    <title></title>
</head>
<body>
<style type="text/css">
    #mask {
        position: fixed;
        z-index: 999;
        width: 100%;
        height: 100%;
        background: #000;
        opacity:0.2;
    }
    #loading {
        width: 200px;
        height: 30px;
        line-height: 30px;
        text-align: center;
        position: fixed;
        left: 50%;
        top: 50%;
        transform: translate(-50%, -50%);
        z-index: 999;
        border: solid 1px #000;
        background: #333;
        color:#FFF;
    }
</style>
<script type="text/javascript">
    window.addEventListener("load", function(args){
        window.setTimeout(function () {
            document.getElementById("loading").style.display = "none";
            document.getElementById("mask").style.display = "none";
        }, 2000);
    });
</script>
<div id="mask">

</div>
<div id="loading">
loading
</div>
<button onclick="javascript:alert('OK')">Click Me</button>
</body>
</html>

show loading icon until the page is load?

HTML

<body>
    <div id="load"></div>
    <div id="contents">
          jlkjjlkjlkjlkjlklk
    </div>
</body>

document.onreadystatechange = function () {
  var state = document.readyState
  if (state == 'interactive') {
       document.getElementById('contents').style.visibility="hidden";
  } else if (state == 'complete') {
      setTimeout(function(){
         document.getElementById('interactive');
         document.getElementById('load').style.visibility="hidden";
         document.getElementById('contents').style.visibility="visible";
      },1000);
  }
}

CSS

#load{
    width:100%;
    height:100%;
    position:fixed;
    z-index:9999;
    background:url("https://www.creditmutuel.fr/cmne/fr/banques/webservices/nswr/images/loading.gif") no-repeat center center rgba(0,0,0,0.25)
}

Note:

you wont see any loading gif if your page is loaded fast, so use this code on a page with high loading time, and i also recommend to put your js on the bottom of the page.

DEMO

http://jsfiddle.net/6AcAr/ - with timeout(only for demo)

http://jsfiddle.net/47PkH/ - no timeout(use this for actual page)

update

http://jsfiddle.net/d9ngT/

Display a loading bar before the entire page is loaded

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>

JavaScript Loading Screen while page loads

You can wait until the body is ready:

function onReady(callback) {
  var intervalId = window.setInterval(function() {
    if (document.getElementsByTagName('body')[0] !== undefined) {
      window.clearInterval(intervalId);
      callback.call(this);
    }
  }, 1000);
}

function setVisible(selector, visible) {
  document.querySelector(selector).style.display = visible ? 'block' : 'none';
}

onReady(function() {
  setVisible('.page', true);
  setVisible('#loading', false);
});

body {
  background: #FFF url("https://i.imgur.com/KheAuef.png") top left repeat-x;
  font-family: 'Alex Brush', cursive !important;
}

.page    { display: none; padding: 0 0.5em; }
.page h1 { font-size: 2em; line-height: 1em; margin-top: 1.1em; font-weight: bold; }
.page p  { font-size: 1.5em; line-height: 1.275em; margin-top: 0.15em; }

#loading {
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  z-index: 100;
  width: 100vw;
  height: 100vh;
  background-color: rgba(192, 192, 192, 0.5);
  background-image: url("https://i.stack.imgur.com/MnyxU.gif");
  background-repeat: no-repeat;
  background-position: center;
}

<link href="https://cdnjs.cloudflare.com/ajax/libs/meyer-reset/2.0/reset.min.css" rel="stylesheet"/>
<link href="https://fonts.googleapis.com/css?family=Alex+Brush" rel="stylesheet">
<div class="page">
  <h1>The standard Lorem Ipsum passage</h1>
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure
    dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p>
</div>
<div id="loading"></div>

How to show Page Loading html file until the page has finished loading?

.load( url [, data ] [, complete ] ) $.load

$(window).load(function(){
  $("body").load("loader.html", function(){
    /* place code need to executed after loader.html load */
  });
});