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const fs = require('fs');
// Read a file asynchronously and pass a callback function to handle the result
fs.readFile('/path/to/file.txt', function(err, data) {
if (err) {
console.error(err);
return;
}
console.log(data);
});
console.log('Reading file...');
In this example, the fs.readFile() function is used to read a file asynchronously. The function takes two arguments: the path to the file and a callback function to handle the result. The callback function is executed when the file has been read, and takes two arguments: an error object (if an error occurred) and the contents of the file.
In the code above, the callback function checks for errors and logs the file contents to the console. Because fs.readFile() is an asynchronous function, the console.log('Reading file...') statement is executed immediately, before the file has been read. Once the file has been read, the callback function is executed, and the file contents are logged to the console.
Callbacks are a powerful and flexible feature of Node.js that allow developers to write asynchronous code that is easy to read and maintain. They are used extensively throughout the Node.js ecosystem, particularly for handling I/O operations and working with APIs that require asynchronous communication.
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