JSFiddle - React, Tailwind, and code Playground

JavaScript

function convertObj(formula) {
   return function (obj) {
        return eval(formula);
    };
}

function convertObj2(formula) {
  return new Function("obj", "return " + formula);
}

var inst = {
      "name": "BOB",
      "age": "30"    
    };

var formula = "obj.name.toLowerCase() + ' is ' + obj.age + ' years old'";

var next = convertObj(formula);
var next2 = convertObj2(formula);

document.write('<p>' + next(inst) + '</p>');
document.write('<p>' + next2(inst) + '</p>');