Callbacks & Callback Hell

What pattern does this code demonstrate?

function fetchData(callback) {
  setTimeout(() => {
    try {
      const data = {id: 1};
      callback(null, data);
    } catch (error) {
      callback(error, null);
    }
  }, 1000);
}

Promise pattern
Error-first callback pattern
This demonstrates the Error-first callback pattern, a standard in Node.js and many JavaScript libraries. Key characteristics: 1) First parameter is reserved for an error object (null if no error), 2) Subsequent parameters contain the success data, 3) Consistently handles both success and error cases, 4) Allows for standardized error handling across asynchronous operations. This pattern is crucial for proper error propagation in callback-based code.
Event emitter pattern
Observer pattern

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