Every programmer knows very well the great effort and the amount of time it takes to make a good source code; Therefore, if they give it to you already partially done, then it is a great help.
JS Slider is a Javascript library (written in pure DHTML and Javascript) that generates everything you need to create all kinds of vertical and horizontal scroll bars on your websites or programs. The programmer will simply have to reference each JS Slider function in Javascript indicating the type of image he wants, the color, the size, and so on.
On the other hand, from the JS Slider functions you can also control if the bar is moved, if a value is entered, if the mouse wheel is moved, and so on.
You can free download JS Slider 32, 64 bit and safe install the latest trial or new full version for Windows 10 from the official site.