nodejsHow to use transform streams

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

let input = fs.createReadStream('/var/www/examples/test.txt');

const my_transform = new Transform({
  transform(chunk, encoding, callback) {
    callback(null, 'TRANSFORMED: ' + chunk.toString());
  },
});

my_transform.on('data', buf => console.log(buf.toString()));

input.pipe(my_transform);ctrl + cgithub

`require('fs')` library to work with file system	`fs.createReadStream(` create stream to read data from (file in our case)
`new Transform(` create new stream that transforms data	`transform(chunk, encoding, callback)` chunk transformation function
`'TRANSFORMED: ' + chunk.toString()` return transformed chunk to callback (we add `TRANSFORMED:` text to chunk as transformation example)	`.on('data'` handle date reading from stream
`.pipe(` pipe object to the given stream (read from file and pipe to transforming stream)

Usage example

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

let input = fs.createReadStream('/var/www/examples/test.txt');

const my_transform = new Transform({
  transform(chunk, encoding, callback) {
    callback(null, 'TRANSFORMED: ' + chunk.toString());
  },
});

my_transform.on('data', buf => console.log(buf.toString()));

input.pipe(my_transform);

output

TRANSFORMED: hi!

More of Nodejs

See more codes...

nodejsHow to use transform streams

Usage example

output

Related

More of Nodejs