Mastering Immutable.js

Iterating over collections and writing lines

Let's start by iterating over a collection and writing each value as a line to an output file:

const myList = Range()  .map(v => `Value${v}`)  .take(20)  .toList();const output = fs.createWriteStream(  './output/05-writing-collection-data');output.on('close', () => {  console.log('done');});myList.forEach((v) => {  output.write((v + os.EOL));});output.end();

The values that we're trying to write to a file are simple strings from myList. The output stream is ready for writing as soon as it's created with fs.createWriteStream(). In the side-effect we've created with forEach(), we're writing each value from the collection to the output stream using the write() method. When the forEach() loop exits, we signal ...