JSFiddle - React, Tailwind, and code Playground

HTML

<input class="etape btn-info others">
<input class="etape btn-inverse others">
<input class="etape btn-danger others">

JavaScript

$(".etape").click(function(){
   var get = $.grep(this.className.split(" "), function(v, i){
       return v.indexOf('btn') === 0;
   }).join();
    console.log(get);
});