In Node.js, callbacks enable asynchronous, non-blocking execution, while methods like readFileSync() perform blocking operations. The fs module provides both synchronous and asynchronous approaches to handle file system tasks.
- Callback Function: Executes after a task completes, enabling non-blocking processing.
- Improves Scalability: Allows handling multiple requests without waiting for operations to finish.
- readFileSync(): A synchronous method that blocks execution until the file is fully read.
- Asynchronous Methods: Continue execution while file operations run in the background.
Example: Code for reading a file synchronously (blocking code) in Nodejs. Create a text file inputfile1.txt with the following content:
Hello Programmer!!!
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// Write JavaScript code
const fs = require("fs");
const filedata = fs.readFileSync('inputfile1.txt');
console.log(filedata.toString());
console.log("End of Program execution");
Output:
- The fs library is used to perform file system operations in Node.js.
- The fs.readFileSync() method reads the file synchronously and blocks execution until the file is completely read.
- The file content is printed before "End of Program execution" because the next statement executes only after readFileSync() completes.
Example : Code for reading a file asynchronously (non-blocking code) in Nodejs. Create a text file inputfile1.txt with the following content.
Hello Programmer!!!
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// Write a JavaScript code
const fs = require("fs");
fs.readFile('inputfile1.txt',
function (ferr, filedata) {
if (ferr) return console.error(ferr);
console.log(filedata.toString());
}
);
console.log("End of Program execution");
Output:
- The fs.readFile() function reads the file asynchronously (non-blocking).
- The program does not wait for the file to be read.
- "End of Program execution" is printed first.
- The file content is printed later when the callback runs.
