JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="one">
	<input type="text" id="two">
	
	<button type="button" id="plus">+</button>
	<button type="button" id="minus">-</button>
	<button type="button" id="multiply">*</button>
	<button type="button" id="divide">/</button>

JavaScript

window.onload = function () {
	var one, two, plusBtn, minusBtn, multiplyBtn, divideBtn, result;
	plusBtn = document.getElementById('plus');
	minusBtn = document.getElementById('minus');
	multiplyBtn = document.getElementById('multiply');
	divideBtn = document.getElementById('divide');


	function values () {
		one = Number(document.getElementById('one').value);
		two = Number(document.getElementById('two').value);
	}


var Calculate = function () {
	this.plus = function () {
		values();
		result = one + two;
		alert('наш результат ' + result);
	};

	this.minus = function () {
		values();
		result = one - two;
		alert('наш результат ' + result);
	};

	this.multiply = function () {
		values();
		result = one * two;
		alert('наш результат ' + result);
	};
	
	this.divide = function () {
		values();
		result = one / two;
		alert('наш результат ' + result);
	};
};

var plusFnc      = new Calculate();
var minusFnc     = new Calculate();
var multiplyFnc  = new Calculate();
var divideFnc    = new Calculate();


plusBtn.onclick = function () {
		plusFnc.plus();
	};

minusBtn.onclick = function () {
		minusFnc.minus();
	};

multiplyBtn.onclick = function () {
		multiplyFnc.multiply();
	};

divideBtn.onclick = function () {
		divideFnc.divide();
	};

};