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

$('input[class]').click(function(){  
 var myClass;
   // classNames will contain all applied classes
   var classNames = $(this).attr('class').split(/\s+/);  
      // iterate over all class  
     $.each(classNames, function(index, item) {
        // Find class that starts with btn-
        if(item.indexOf("btn-") == 0){
          // Store it
          myClass = item;
            alert(myClass);
        }
     });
  
 
});