changeThing.js

function main() {
  const x = getAThing();

  const valueBefore = x.value;
  someOtherFunction();
  const valueAfter = x.value;

  console.log(
    valueBefore === valueAfter // false
  );
}

const thing = {
  value: 3,
};

function getAThing() {
  return thing;
}

function someOtherFunction() {
  thing.value++;
}

main();