Compare callbacks, Promises, and async/await in Node.js. What is callback hell and how do you avoid it?

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## 1. Callbacks A callback is a **function passed as an argument** to be executed later. ```javascript fs.readFile('file.txt', 'utf8', (err, data) => { if (err) { console.error('Error:', err); return; } console.log(data); }); ``` **Error-first pattern**: First argument is always…