Easy stream filters for, say, file read streams/pipes

streamFilter.js

/**
 * Easy stream filters for, say, file read streams/pipes
 */

const stream = require('stream')

class StreamFilter extends stream.Transform {
    constructor(filterCallback) {
        super({
            readableObjectMode: true,
            writableObjectMode: true
        })
        this.filterCallback = filterCallback;
    }
    _transform(chunk, encoding, next) {
        if (this.filterCallback(chunk)) {
            return next(null, chunk)
        }
        next()
    }
}

const streamFilter = filterCallback => new StreamFilter(filterCallback);

module.exports = streamFilter;

// function test () {
//     const fs = require('fs');
//     const csv = require('csv');
//
//     const StreamFilter = require('./src/lib/StreamFilter');
//
//     const src = __dirname + "/src.tsv";
//     const dest = __dirname + "/test.csv";
//
//     const srcStream = fs.createReadStream(src);
//     const destStream = fs.createWriteStream(dest);
//
//     srcStream
//         .on('end', () => console.log('CSV file successfully processed'))
//         // .on('data', (row) => console.log(row))
//         .pipe(csv.parse({delimiter: "\t"}))
//         .pipe(streamFilter(cols => cols[0].includes('magicKeyword')))
//         .pipe(csv.transform(cols => (
//             [
//                 cols[3],
//                 cols[1],
//                 cols[2],
//             ]
//         )))
//         .pipe(csv.stringify())
//         .pipe(destStream)
// }