JSFiddle - React, Tailwind, and code Playground

HTML

<input id="txtbox1">
<input id="txtbox2">
<input type="button" value="Click me" id="btn1">

JavaScript

$(function(){
    $('#btn1').click(function(){
var repl1 = "(GP1/(GP1 + GP2))*100%";
var repl2 = repl1.replace(/GP1/gi,parseInt($("#txtbox1").val()));
var repl3 = repl2.replace(/GP2/gi,parseInt($("#txtbox2").val()));
var repl4 = repl3.replace(/%/gi,"");
    alert(repl4);
        alert(eval(repl4));
    });
});