Spot the Bug - N_02 | khriztianmoreno's Blog

Bug hunters, assemble! We have a new challenge for you. This JavaScript code snippet is supposed to enrich a list of events with user metadata. But, is everything working as it should?

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));

Your mission:

Find the bug: There’s a small error preventing the code from working correctly. Can you spot it?
Explain it: Once you’ve found the issue, explain why you think it’s a bug and what the correct solution would be.
Suggest improvements: If you see anything that could be optimized or improved in the code, feel free to share your suggestions!

Accept the challenge and show off your debugging skills!

🚀 Solution 👩🏻‍💻🐛👨🏼‍💻

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));

Spot the Bug - N_02

@khriztianmoreno 🚀