Push chunk to nodejs stream on demand

push_chunk_to_nodejs_stream_on_demand.js

//we could avoid buffering data altogether and only generate the data when the consumer asks for it.
//We can push chunks on-demand by defining a ._read function

//To show that our _read function is only being called when the consumer requests,
//we can modify our readable stream code slightly to add a delay:
var Readable = require('stream').Readable;
var rs = Readable();

var c = 97 - 1;

rs._read = function () {
    if (c >= 'z'.charCodeAt(0)) return rs.push(null);
    
    setTimeout(function () {
        rs.push(String.fromCharCode(++c));
    }, 100);
};

rs.pipe(process.stdout);

process.on('exit', function () {
    console.error('\n_read() called ' + (c - 97) + ' times');
});
process.stdout.on('error', process.exit);