mSelect by Damion Mullins

Instructions:

Download mSelect.js and mSelect.css
Add both files and JQuery (3.3.1 tested) to your website as you would any other JS and CSS files
Inject mSelect into your listboxes by adding $("#yourSelectId").mSelect();
Post to a server as normal. mSelect simply manipulates the original select listbox where the actual values are located.

There are 3 styling configurations you can make to mSelect:


        $("#yourSelectId").mSelect(
            {
                "dropDownHeight": an integer, // defualt is 200 (in pixles)
                "popUpHeight": an integer, // defualt is 200 (in pixles)
                "placeholder": "Any text" // defualt will use the option with no value or 0 value
            }
        );

To remove (destroy) mSelect and restore the original select listbox, just add "destroy" as the parameter:


        $("#yourSelectId").mSelect('destroy');

You do not have to destroy and rebuild mSelect whenever changes are made to your original select listbox. Instead, just re-inject mSelect to the select listbox at anytime:


        // Example of modifying your original select listbox, and then updating mSelect
        $("#yourSelectListbox")
            .append("<option value='newOption'>New Option</option>")
            .mSelect();

To execute an event after a change was made in the mSelect listbox, add the following configuration:


        $("#yourSelectId").mSelect(
            {
                onAfterChange: function() {
                    // add your function here
                }
            }
        );

To make mSelect readonly (disabled):


        $("#yourSelectId").mSelect(
            {
                "readonly":1, // must be 1 in order for it to be readonly
                "readonlyMinWidth": an integer // default is 300 pixels
            }
        );

	HTML Select Listbox	mSelect
Single select listbox example
Multi-select listbox example
Multi-select listbox with option groups example
Single select listbox with disabled options example
Items pre-selected and in readonly mode