JSFiddle - React, Tailwind, and code Playground

HTML

<button id="myButton">Click</button>

JavaScript

function example1(){
    this.state = {a: 1};
    
    $('#myButton').on('click', function(){
       // this will be the element myButton which has no state.
       console.log(this.state);  // undefined
    });
}

function example2(){
    this.state = {a: 1};
    
    $('#myButton').on('click', (function(){
        // since we binded this, it will log the state always no madder who the caller is.
       console.log(this.state); 
    }).bind(this));
}

var ex1 = new example1();
var ex2 = new example2();