Split JS is a small jQuery plugin that allows you to split an html element vertically or horizontally with a handle to adjust the size.

How to use:

<div id="split1">
                <div class="split-component-1" style="width: 100px;">
            	    First Half
                </div>
                <div class="split-component-2">
            	    Second Half
                </div>
</div>

Then use:

$("#split1").splitIt("vertical");

Visit the github page for a demo here