JSFiddle - React, Tailwind, and code Playground

HTML

<form method="post">
    <input name="mycheckgroup" type="checkbox" value="1"  />
		<input name="mycheckgroup" type="checkbox" value="2"  /> 
		<input name="mycheckgroup" type="checkbox" value="3"  />
		<input type="submit" id="btnSubmit" value="submit" />
</form>

JavaScript

$("#btnSubmit").click(function(e){
				if( $("input[name=mycheckgroup]:checked").length == 0){
					$("input[name=mycheckgroup]:first").attr("required", "required");
				}else{
					$("input[name=mycheckgroup]").removeAttr("required");				
					$("form").submit();
				}			
			});