JSFiddle - React, Tailwind, and code Playground

JavaScript

// in an easy to call function:
    function getPropertyByRegex(obj,propName) {
       var helloRE = new RegExp("^" + propName + "(\\[\\d*\\])?$"),
           key;
       for (key in obj)
          if (helloRE.test(key))
             return obj[key];
       return null; // put your default "not found" return here
    }

    var foo = {"hello[35]":100,"goodbye[45]":42};

    alert(getPropertyByRegex(foo, "hello"));    // 100
    alert(getPropertyByRegex(foo, "goodbye"));  // 42
    alert(getPropertyByRegex(foo, "whatever")); // null (not found)