lines.js

/**
 Instead of transforming every line as in the previous "INPUT OUTPUT" example,
 for this challenge, convert even-numbered lines to upper-case and odd-numbered
 lines to lower-case. Consider the first line to be odd-numbered. For example
 given this input:

 One
 Two
 Three
 Four

 Your program should output:

 one
 TWO
 three
 FOUR

 You can use the `split` module to split input by newlines. For example:

 var split = require('split');
 process.stdin
 .pipe(split())
 .pipe(through(function (line) {
            console.dir(line.toString());
        }))
 ;

 Will buffer and split chunks on newlines before you get them. For example, for
 the `split.js` we just wrote we will get separate events for each line even
 though the data probably all arrives on the same chunk:

 $ echo -e 'one\ntwo\nthree' | node split.js
 'one'
 'two'
 'three'

 Your own program should use `split` in this way, but you should transform the
 input and pipe the output through to `process.stdout`.

 */

var through = require('through');
var split = require('split');

var write = function(data) {
	cnt++;
	if (cnt % 2 == 0) {
		this.queue(data.toString().toUpperCase()+"\n");
	}
	else {
		this.queue(data.toString().toLowerCase()+"\n");
	}

}

var tr = through(write);
var cnt = 0;

process.stdin.pipe(split()).pipe(tr).pipe(process.stdout);