read-file.js

/**
 * Creates an asynchronous ReadStream for the file whose name
 * is `fileName` and feeds it into an AsyncQueue that it returns.
 *
 * @returns an async iterable
 */
function readFile(fileName) {
    const queue = new AsyncQueue();
    const readStream = createReadStream(fileName,
        { encoding: 'utf8', bufferSize: 1024 });
    readStream.on('data', buffer => {
        const str = buffer.toString('utf8');
        queue.enqueue(str);
    });
    readStream.on('end', () => {
        // Signal end of output sequence
        queue.close();
    });
    return queue;
}