JSFiddle - React, Tailwind, and code Playground

HTML

<label> Lastname * </label>

CSS

.red{
    color: #ff0000;
}

JavaScript

$(function(){
    
    var elements = $('label');
    var markup_element = $('<span class="red">*</span>');
    
    elements.each(function(){
        
        //wrap the element in a jquery object and get it's text string
            var element = $(this);    
            var element_text = element.text();
        
        //use regex to use the * as a delimeter
            var other_parts = element_text.split(/\*/);
                
        //empty the element re-add each part programmatically
            element.empty();
            for( var i = 0; i < other_parts.length; i++ ){
                element.append( other_parts[i] );
                if( i != other_parts.length - 1 ){
                    element.append( markup_element );
                }
            }
            
    });
    
});