JSFiddle - React, Tailwind, and code Playground

HTML

<div id="target" style="width:150px;height:150px;background:red;">
    Test
</div>
<input type="button" value="test" id="btn" />

JavaScript

$.fn.myFadeIn = function(){
    this.show();
    this.css("opacity",0);
    for(var i = 0 ; i < 100 ;++ i){
       this.css("opacity", i );        
    }
    this.html("fadeIn invoked");
}
    
$("#btn").click(function(){
   $("#target").myFadeIn();//invoking the $.fn.myFadeIn
});