How to prevent fixed button from overlapping footer area and stop the button on top of where the footer is located

Question

I am trying to create a button that is fixed on the lower-left side of the screen. I tried to setup in JSFiddle to recreate what I'm trying to do.

Here is my HTML:

<div id="header">header
</div>
<div id="button">button
</div>
<div id="content">some content
</div>
<div id="footer">footer
</div>

And the CSS:

#header,#footer{
background-color:red;



}
#content
{
    height:2000px;
}
#footer
{
    height:200px;
}
#button
{
    background-color:gray;
    width:100px;
    height:100px;
    position:fixed;
    bottom:0;
    left:0;
    right:0;    
}

I have read that, I should use plugins such as scrolltoFixed.js, lockfixed.js but my problem is I don't know how to use or even where to start editing the javascript. Here is a fiddle

I want the button to stop where the footer is, and make it like it was docked.

Answer 1

Updated now so that it sticks above footer.

Hope this is what you meant The jQuery:

$(window).scroll(function() {
   if($(window).scrollTop() + $(window).height() > $(document).height() - 200) {
       $('#button').addClass('fixed_button');
   }else{
       $('#button').removeClass('fixed_button');
   }
});

CSS:

.fixed_button{
    position:absolute !important;
    margin-top:1900px;
    bottom: auto !important;
}