challenge1.js

var fs = require("fs");
var	file = "file.txt",
	sum = 0,
	chars = [];

/// @summary: aggregate values
function aggregater(value) {
	if (parseInt(value, 10).toString() === value.toString()) {
		sum += parseInt(value, 10);
		return;
	}
	chars[value] = typeof(chars[value]) === 'undefined' ? 1 : chars[value] + 1;
}

/// @summary: print values
function printer() {
	console.log("Sum = " + sum);
	for (i in chars)
		if (chars.hasOwnProperty(i)) console.log(i + ' = ' + chars[i]);
}

// create stream
var stream = fs.createReadStream(file, {
	  'flags': 'r'
	, 'encoding': 'utf8'
	, 'mode': 0666
	, 'bufferSize': 2
});

// @summary: listen for incoming data to aggregate
stream.addListener("data", function(data) {
	aggregater(data.toString().replace("\n", ""));
});

// @summary: file done streaming, print results
stream.addListener("end", function() {
	printer();
});