JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/ui-lightness/jquery-ui.css">
<div id='x' data-image-x-offset='50px'>

JavaScript

var key = 'imageXOffset';

var rmultiDash = /([a-z])([A-Z])/g;

var name = "data-" + key.replace( rmultiDash, "$1-$2" ).toLowerCase();

alert( name );