Node.js Streams

🌊 Node.js – Streams

Streams are objects in Node.js that allow reading or writing data in chunks, instead of loading the entire data into memory.
This is memory-efficient and suitable for large files.

Streams are event-based and work with EventEmitter.

✅ 1. Types of Streams

Type	Description	Example
Readable	Stream you can read data from	`fs.createReadStream()`
Writable	Stream you can write data to	`fs.createWriteStream()`
Duplex	Both readable and writable	TCP sockets
Transform	Modify data while reading/writing	`zlib.createGzip()`

✅ 2. Readable Streams

Used to read data in chunks.

const fs = require("fs");

const readStream = fs.createReadStream("input.txt", "utf8");

readStream.on("data", (chunk) => {
console.log("Chunk received:", chunk);
});

readStream.on("end", () => {
console.log("Finished reading file");
});

readStream.on("error", (err) => {
console.log("Error:", err);
});

const fs = require("fs");

const readStream = fs.createReadStream("input.txt", "utf8");

readStream.on("data", (chunk) => {

console.log("Chunk received:", chunk);

});

readStream.on("end", () => {

console.log("Finished reading file");

});

readStream.on("error", (err) => {

console.log("Error:", err);

});

✅ 3. Writable Streams

Used to write data in chunks.

const fs = require("fs");

const writeStream = fs.createWriteStream("output.txt");

writeStream.write("Hello Node.js Streams\n");
writeStream.write("Writing another line\n");
writeStream.end("Finished writing!"); // signals end

writeStream.on("finish", () => {
console.log("All data written successfully!");
});

writeStream.on("error", (err) => {
console.log("Error:", err);
});

const fs = require("fs");

const writeStream = fs.createWriteStream("output.txt");

writeStream.write("Hello Node.js Streams\n");

writeStream.write("Writing another line\n");

writeStream.end("Finished writing!"); // signals end

writeStream.on("finish", () => {

console.log("All data written successfully!");

});

writeStream.on("error", (err) => {

console.log("Error:", err);

});

✅ 4. Pipe Streams

You can pipe data from a readable stream to a writable stream easily.

✅ Automatically handles data events and writes data efficiently.

✅ 5. Transform Streams

Used to modify data while reading/writing.

Example: Convert text to uppercase.

const { Transform } = require("stream");

const upperCase = new Transform({
transform(chunk, encoding, callback) {
this.push(chunk.toString().toUpperCase());
callback();
}
});

const fs = require("fs");

fs.createReadStream("input.txt")
.pipe(upperCase)
.pipe(fs.createWriteStream("output.txt"));

const { Transform } = require("stream");

const upperCase = new Transform({

transform(chunk, encoding, callback) {

this.push(chunk.toString().toUpperCase());

callback();

}

});

const fs = require("fs");

fs.createReadStream("input.txt")

.pipe(upperCase)

.pipe(fs.createWriteStream("output.txt"));

✅ 6. Duplex Streams

Both readable and writable.

Example: TCP socket (simplified):

const { Duplex } = require("stream");

const duplex = new Duplex({
read(size) {},
write(chunk, encoding, callback) {
console.log("Writing:", chunk.toString());
callback();
}
});

duplex.write("Hello Duplex!");
duplex.on("data", (chunk) => console.log("Read:", chunk.toString()));

const { Duplex } = require("stream");

const duplex = new Duplex({

read(size) {},

write(chunk, encoding, callback) {

console.log("Writing:", chunk.toString());

callback();

}

});

duplex.write("Hello Duplex!");

duplex.on("data", (chunk) => console.log("Read:", chunk.toString()));

✅ 7. Event Listeners in Streams

Event	Description
`data`	Triggered when a chunk is available (Readable)
`end`	Triggered when all data is read
`error`	Triggered when an error occurs
`finish`	Triggered when writing is complete (Writable)
`pipe`	Triggered when piping starts
`unpipe`	Triggered when piping stops

✅ 8. Example: Read + Transform + Write Stream

const fs = require("fs");
const { Transform } = require("stream");

const transformStream = new Transform({
transform(chunk, enc, callback) {
this.push(chunk.toString().toUpperCase());
callback();
}
});

fs.createReadStream("input.txt")
.pipe(transformStream)
.pipe(fs.createWriteStream("output.txt"));

const fs = require("fs");

const { Transform } = require("stream");

const transformStream = new Transform({

transform(chunk, enc, callback) {

this.push(chunk.toString().toUpperCase());

callback();

}

});

fs.createReadStream("input.txt")

.pipe(transformStream)

.pipe(fs.createWriteStream("output.txt"));

🎯 Advantages of Streams

Efficient memory usage
Handle large files without crashing
Supports piping & chaining
Real-time processing of data
Works well with network operations

Node.js Streams

🌊 Node.js – Streams

✅ 1. Types of Streams

✅ 2. Readable Streams

✅ 3. Writable Streams

✅ 4. Pipe Streams

✅ 5. Transform Streams

✅ 6. Duplex Streams

✅ 7. Event Listeners in Streams

✅ 8. Example: Read + Transform + Write Stream

🎯 Advantages of Streams

You may also like...

Node.js Tutorials

Node.js Streams

🌊 Node.js – Streams

✅ 1. Types of Streams

✅ 2. Readable Streams

✅ 3. Writable Streams

✅ 4. Pipe Streams

✅ 5. Transform Streams

✅ 6. Duplex Streams

✅ 7. Event Listeners in Streams

✅ 8. Example: Read + Transform + Write Stream

🎯 Advantages of Streams

You may also like...

Node.js Assert Module

Node.js Crypto Module:

Node.js Buffer Module

Node.js Tutorials