JSFiddle - React, Tailwind, and code Playground

HTML

<div id='myDiv' style="border: 1px, solid, black"> Click me!! </div>

JavaScript

var Constructor = function (name, value) {
    var self = this;
    
    self.name = name;
    self.value = value;
};

Constructor.prototype.someHandler = function (e) {
    e.target.innerHTML = self.name + self.value; // self undefined
    e.target.innerHTML = this.name + this.value; // this refers to the DOM object
};

var myObject = new Constructor('myName', 'myValue');
document.getElementById('myDiv').onclick = myObject.someHandler;