JSFiddle - React, Tailwind, and code Playground

JavaScript

var lt = {
 "part1" : "p1",
 "part2" : "p2",
 "part3" : "p3"
};

var myVar = "part2";
var z;

if (typeof lt[myVar] !== "undefined") {
  z = lt[myVar];
}

console.log(z);

//second option:
var z2;

if (myVar in lt) {
  z2 = lt[myVar];
}

console.log(z2);