Most likely your IDE would catch this one for you, but there is a syntax error. The map function is an arrow function that implicitly returns the result of the expression inside the block. In this case, the block is not a valid expression, so the code will throw a syntax error. To fix this, you can wrap the object in parentheses to make it an expression.

const enrichEvents = (events) => {
  const metadata = {
    usr_789: { tier: "premium", joined: "2023-04-01" },
  };

  const enriched = events.map((event) => ({
    id: event.id,
    time: event.time,
    user: metadata[event.userId],
    value: event.properties.totalValue,
  }));

  return enriched;
};

const events = [
  {
    id: "evt_123",
    time: "2024-12-10T10:00:00Z",
    userId: "usr_789",
    properties: {
      totalValue: 99.99,
    },
  },
];

console.log(enrichEvents(events));