Problems with "internal" mutability

buidCallbacks.js

const buildCallbacks = items => {
  const callbacks = [];
  let i;
  for (i = 0; i < items.length; i++) {
    callbacks.push(() => items[i]);
  }
  return callbacks;
}

const callbacks = buildCallbacks(["hello", "cruel", "world"]);

callbacks.length; // => 3
callbacks[0](); // => undefined
callbacks[1](); // => undefined
callbacks[2](); // => undefined