JSFiddle - React, Tailwind, and code Playground

by Rajesh Dixit

HTML

<input class="tdinput" type="text" data-key="c1">
<input class="tdinput" type="text" data-key="d2">

<input type="text" data-formula="(c1 + d2)">
<button id="btnCalculate">calculate</button>

JavaScript

$("#btnCalculate").on("click", function() {
   var $f = $("input[data-formula]");
   var formula = $f.data("formula");
   formula.split(/[^a-z0-9]/gi)
      .forEach(function(el) {
         if (el) {
            let v = $("[data-key='" + el + "']").val();
            formula = formula.replace(el, v);
         }
      });

   var result = eval(formula);
   console.log(result)
   $f.val(result)
})