Some code to show events in stream

src_data.txt

example text data to copy from

execute
> node stream-to-target.spec.js

to read:
"""
read stream end
write stream finish ./tgt_data.txt
read stream close
write stream close ./tgt_data.txt
success ./tgt_data.txt
data
"""

stream-to-target.js

const fs = require('fs')

const streamToTarget = (stream, targetFile) => new Promise((resolve,reject) => {
    stream.on('end', ()=> {
        console.log('read stream end');
        //resolve(targetFile);
    });
    stream.on('close', ()=> {
        console.log('read stream close');
        //resolve(targetFile);
    });
    stream.on('error',(err) => {
        console.log('read stream error',err)
        reject(`error on read stream ${err.toString()}`);
    })
    let ws_target = fs.createWriteStream(targetFile)
    ws_target.on('error', (err) => {
        console.log('write stream err',err)
        reject(`error on stream target stream ${targetFile} ${err.toString()}`);
    })

    ws_target.on('finish', ()=> {
        console.log(`write stream finish ${targetFile}`);
        //resolve(targetFile);
    });
    ws_target.on('close', ()=> {
        console.log(`write stream close ${targetFile}`);
        resolve(targetFile);
    });

    stream.pipe(ws_target);
})

module.exports = streamToTarget;

stream-to-target.spec.js

const fs = require('fs')

const streamToTarget = require('./stream-to-target');
const source = './src_data.txt';
const target = './tgt_data.txt'
let stream = fs.createReadStream(source);


setTimeout(()=>console.log('data'), 2000);

return streamToTarget(stream,target)
.then(msg=>console.log(`success ${msg}`))
.catch(err=>console.error(`error: ${err}`));

setTimeout(()=>console.log('data'), 2000);

Why this line?

setTimeout(()=>console.log('data'), 2000);

Why this line?

just to cheer "data". No, just to print something at the end, I am assuming here that 2 second is enough to make the work.

The only point here were to show that when using .pipe() read stream end, then write stream finish, then read stream close, then write stream close. And this sequence make sense