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Error-First Callbacks - Asynchronous JavaScript | JavaScript | Repovive

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JavaScript22 sections · 783 units18h total

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Error-First Callbacks

Node.js callback convention

Node.js uses error-first callbacks. The first parameter is an error (or null if success). The second is the result.

readFile("data.txt", (err, data) => {
  if (err) {
    console.error("Failed:", err);
    return;
  }
  console.log(data);
});

Always check the error parameter first before using the result.