javascript - Bring an element to top of the page even if the page does not scroll - Stack Overflow

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Background:

Let's say you have a simple page which has a logo and a heading only and one paragraph

<img src=".png">
<h1>Foo Bar</h1>
<p>ABC12345</p>

This is how that looks like

That page, obviously would not have vertical overflow / scroll bar for almost even tiny scale mobile devices, let alone puters.

Question

How can you bring that heading to the top left of the screen and move the logo out of focus unless someone scrolls up? Open to using any JavaScript library and any CSS framework

Attempts:

1. Tried using anchors but they only work if the page already had a scroll bar and anchor was out of focus.
2. Tried window.scrollTo but that also requires the page to have scroll already
3. Tried $("html, body").animate({ scrollTop: 90}, 100); but that also doesn't work when the page doesn't have overflow

Notes:

Please note that adding some extra <br/> to induce an overflow is not the way to go, it can be done that way but that's a very ordinary workaround

Why is it needed?

Its for a form for mobile devices, simple requirement is to take the first field of the form to top of the page and hide the logo (one can scroll up if they wish to see it) so it doesn't take attention away. Not using jQueryMobile for this particular task.

Background:

Let's say you have a simple page which has a logo and a heading only and one paragraph

<img src="http://blog.stackoverflow./wp-content/uploads/StackExchangeLogo1.png">
<h1>Foo Bar</h1>
<p>ABC12345</p>

This is how that looks like

That page, obviously would not have vertical overflow / scroll bar for almost even tiny scale mobile devices, let alone puters.

Question

How can you bring that heading to the top left of the screen and move the logo out of focus unless someone scrolls up? Open to using any JavaScript library and any CSS framework

Attempts:

1. Tried using anchors but they only work if the page already had a scroll bar and anchor was out of focus.
2. Tried window.scrollTo but that also requires the page to have scroll already
3. Tried $("html, body").animate({ scrollTop: 90}, 100); but that also doesn't work when the page doesn't have overflow

Notes:

Please note that adding some extra <br/> to induce an overflow is not the way to go, it can be done that way but that's a very ordinary workaround

Why is it needed?

Its for a form for mobile devices, simple requirement is to take the first field of the form to top of the page and hide the logo (one can scroll up if they wish to see it) so it doesn't take attention away. Not using jQueryMobile for this particular task.

• javascript
• jquery
• css

Share Improve this question Follow edited Apr 22, 2014 at 12:51 Hanky Panky asked Apr 21, 2014 at 11:42 Hanky PankyHanky Panky 46.9k99 gold badges7575 silver badges9595 bronze badges 3

• Use this $(window).scroll(function(){if($(window).scrollTop>"the height of your logo"){"Do your stuff here"}}); – Tyranicangel Commented Apr 21, 2014 at 11:56
• You could use media-queries to detect if it is a small screen device. Hide the logo if devices are small. Then, Look for a scroll event and display the logo. – stackErr Commented Apr 23, 2014 at 14:48
• I do not understand what you mean by "Tried window.scrollTo but that also requires the page to have scroll already" can you please clarify this? If you mean the page is not long enough to scroll, then you can look at my answer and I address that issue. – smilebomb Commented Apr 23, 2014 at 16:09

Add a ment  | 

7 Answers 7

Sorted by: Reset to default 5 +100

If you want the user to be able to scroll up and see the logo, then the logo must be within the top boundary of the body tag, because anything outside of that tag will not be viewable. This means you cannot use negative margins or offsetting like that. The only way to achieve this is to have the page scroll to the desired location that is within the top boundary of the body tag. You can set the time for this event to one millisecond, but there will still be a 'jump' in the page when it is loaded. So, the logic is: first make sure the page is long enough to scroll to the right place, then scroll there.

//Change the jQuery selectors accordingly

//The minimum height of the page must be 100% plus the height of the image
$('body').css('min-height',$(document).height() + $('img').height());

//Then scroll to that location with a one millisecond interval
$('html, body').animate({scrollTop: $('img').height() + 'px'}, 1);

View it here.

Alternatively, you can load the page without the image in the first place. Then your form field will be flush with the top of the document. Then you could create the element at the top and similarly scroll the page again. This is a round-a-bout way of doing the same thing though. And the page will still 'jump,' there is no way around that.

Only CSS and anchor link solution

With a pseudo element :

--- DEMO ---

First :

set : html,body{height:100%;}

Second :

Choose one of your existing tags. This tag mustn't have a relatively positioned parent (except if it is the body tag). Preferably the first element in the markup displayed after the logo. For your example it would be the h1 tag. And give it this CSS :

h1:before {
    content:"";
    position:absolute;
    height:100%;
    width:1px;
}

This creates an element as heigh as the viewport area. As it is displayed under the logo, the vertical scroll lenght is the same as the logo height.

Third :

Give the first element after logo an id (for this example I gave id="anchor").

Then you can use a link like this your_page_link#anchor and you will automaticaly scroll to the anchor (logo outside/above the viewport).

This works whatever height the logo is.

link to editable fiddle

Full code :

HTML

<img src="http://blog.stackoverflow./wp-content/uploads/StackExchangeLogo1.png">
 <h1 id="anchor">Foo Bar</h1>

<p>ABC12345</p> <a href="#anchor">Anchor link</a>

CSS

html, body {
    height:100%;
    margin:0;
    padding:0;
}
h1:before {
    content:"";
    position:absolute;
    width:1px;
    left:0;
    height:100%;
}

You might need to add js functionality to hide the logo if user scrolls down but I guess following code will fullfill the first requirement.
Please see

 <script src="js/jquery.js"></script>
 <img id='logo' src="http://blog.stackoverflow./wp-content/uploads/StackExchangeLogo1.png" style="display:none">
 <h1>Foo Bar</h1>
 <p>ABC12345</p>
 <script type="text/javascript">
  var p = $( "p:first" ); 
  var isScrolled=false;
   /* For Firfox*/
   $('html').on ('DOMMouseScroll', function (e) {
     isScrolled = true;
     if(p.scrollTop()==0 && isScrolled==true){
        $('#logo').css('display','block');
      }
   });
   /* For Chrome, IE, Opera and Safari: */
   $('html').on ('mousewheel', function (e) {
      isScrolled = true;
      if(p.scrollTop()==0 && isScrolled==true){
         $('#logo').css('display','block');
      }
   });
  </script>

I have referred this question to find solution.

You could use touchmove event to detect swipe up or down. This is my example. You can try it on mobile device.

  <style>
  #logo {
    position: absolute;
    top: -100%;
    -webkit-transition: top 0.5s;
    -moz-transition: top 0.5s;
    -ms-transition: top 0.5s;
    -o-transition: top 0.5s;
    transition: top 0.5s;
  }
  #logo.show {
      top: 0;
  }
  </style>

  <script>
  var perY;
  var y;
  $(window).on('touchmove', function(e) {
    e.preventDefault();
    y = window.event.touches[0].pageY;
    if(!perY)
      perY = y;
    else
    {
      if(y > perY)
        $('#logo').addClass('show');
      else
        $('#logo').removeClass('show');
      perY = null;
    }
  });

  </script>


  <img id="logo" src="http://blog.stackoverflow./wp-content/uploads/StackExchangeLogo1.png">
  <h1>Foo Bar</h1>
  <p>ABC12345</p>

This is the same problem i've encountered hiding the addressbar without the page overflowing. The only solution that fitted my needs was the following:

Set the min-height of the body to the viewportheight + your logo.

$('body').css('min-height', $(window).height() + 200);

This is a simple solution of getting the height of the contents to see if we can scroll to the part of the header, if not, we add height to the paragraph.

<img id="img" src="http://blog.stackoverflow./wp-content/uploads/StackExchangeLogo1.png" />
 <h1 id="h" >Foo Bar</h1>
<p id="par" style="background:yellow;">
   hello world
</p>

script:

function hola(){
   var imgH = $("#img").outerHeight(true);
   var titleH =  $("#h").outerHeight(true);
   var winH = $(window).height();
   var parH = $('#par').outerHeight(true);
   var contH = (imgH + titleH + parH);
   var wishH = (imgH + winH);
   console.log("wished height: " + wishH);
   console.log("window height: " + winH);
   console.log("content height: " + contH);
   if(contH < wishH){
    console.log("window is smaller than desired :(");
    var newH = wishH - contH;
    $("#par").height(parH + newH);
    $(window).scrollTop(imgH);
   }
}

Here is the working example: http://jsfiddle/Uup62/1/

You may like this solution: http://jsfiddle/jy8pT/1/

HTML:

  <div class="addScroll"></div>
  <h1 class="logo"><img src="https://drupal/files/images/OQAAAI1PPrJY0nBALB7mkvju3mkQXqLmzMhxEjeb4gp8aujEUQcLfLyy-Sn4gZdkAas6-k8eYbQlGDE-GCjKfF5gIrUA15jOjFfLRv77VBd5t-WfZURdP9V3PdmT.png" height="100" alt="pany logo"/></h1>

  <h2>This is a sample page heading.</h2>
  <p>This is a sample page text.</p>

JS:

function addScroll()
{
  $(".addScroll").css({
    "height": ($(window).height()+1) + "px",
    "width": "100%"
  });
}

$(document).ready(function(){
addScroll();
  $(window).resize(function(){
    addScroll();
  });
  $(window).scroll(function(){
     if($(window).scrollTop() > 0) 
     {
       $(".logo").animate({
         marginTop: "-110px"
       }, 500);
     }

      if($(window).scrollTop() == 0) 
     {
       $(".logo").animate({
         marginTop: "0"
       }, 500);
     }
  });
});

CSS:

body
{
    padding:0;
    margin:0;
}
h1.logo
{
  display:block;
  margin:0 0 10px 0;
  padding:0;
  outline:0;
}
.addScroll
{
  position:absolute;
  display:block;
  top:0;
  left:0;
  z-index:-1;
}

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