JSFiddle - React, Tailwind, and code Playground

HTML

<button type="button">click</button>

JavaScript

Function.prototype.addMethod = function(name, fn){
	this.prototype[name] = fn;
  return this;
}

var Methods = function(){}


Methods.addMethod('checkName', function(){
	alert(1);
  return this
}).addMethod('checkEmail', function(){
	alert(2);
  return this;
});

var m = new Methods();
m.checkName().checkEmail();