JS How do I keep my sliding div to its position?

See more:

Javascript

Hello,
I am working on a slideshow with thumbnails.
My slideshow works but I'd like to have an horizontal slide of my thumbnail since I don't have enough space to display them all.
It could be on hover or on click of a button prev/next. My code needs to be in javascript only no librairies.

My HTML

<div class="controls">
	<a class="previous" href="" id="prev" ><img src="images/fleche_g.jpg" alt="Voir les vignettes de gauche" title="Voir les vignettes de gauche" /></a>
	<div class="wrapper-thumbs">
		<div id="allthumbs">
			<ul id="thumbs">
			</ul>
		</div>
	</div>
	<a class="next" href="" id="next" ><img src="images/fleche_d.jpg" alt="Voir les vignettes de droites" title="Voir les vignettes de droites" /></a>
</div>

My CSS

#slideshow .controls .wrapper-thumbs {
	overflow: hidden;
	position: relative;
	float: left;
	margin: 0;
	width: 556px;
	height: 76px;
}
 
/* #allthumbs {
	width: 556px;
	overflow-x: auto;
	overflow-y: hidden;
	white-space: nowrap;
} */
 
#thumbs {
	display: inline-block;
	width: 900px;
	height: 76px;
	position: absolute;
	z-index: 99;
}
 
#thumbs li {
	display: inline-block;
	max-width: 114px;
	margin-left: 10px;
}
 
#thumbs img {
	float: left;
	width: 114px;
	margin: 0;
}
 
#thumbs img:hover {
	cursor: pointer;
}
 
#slideshow .controls .previous, #slideshow .controls .next {
	float: left;
	width: 51px;
	height: 76px;
	position: relative;
	z-index: 999;
}
 
#slideshow .controls .previous {
	background: transparent url('images/fleche_g.jpg') 0 0 no-repeat;
}
 
 
#slideshow .controls .next {
	background: transparent url('images/fleche_d.jpg') 0 0 no-repeat;
}

My JS

// Use the arrow to slide the thumbnails
	var chrono;
	function stopChrono() {
	    clearInterval(chrono);
	}
	 
	function left() {
	    document.getElementById("allthumbs").scrollLeft = (parseInt(document.getElementById("allthumbs").scrollLeft,10) - 10);
	    chrono = setTimeout("left()",100);
	}
	 
	function right() {
	    document.getElementById("allthumbs").scrollLeft = (parseInt(document.getElementById("allthumbs").scrollLeft,10) + 10);
	    chrono = setTimeout("right()",100);
	}

I can scroll the list of thubnails to the right but then when I mouseup, the list goes back to its original state. I'd like to
- stay where I arrived
- be able to use my left button.

Here is my live example

Can anyone help me?

Thanks !!