# Node.js code snippets

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[[Learning Node.JS Programming]]


## hello-console.js

    // Call the console.log function.
    console.log("Hello World.");


## hello-server.js

    // Load the http module to create an http server.
    var http = require('http');

    // Configure our HTTP server to respond with Hello World to all requests.
        var server = http.createServer(function (request, response) {
        response.writeHead(200, {"Content-Type": "text/plain"});
        response.end("Hello World\n");
    });

    // Listen on port 8080, IP defaults to 127.0.0.1
    server.listen(8080);

    // Put a friendly message on the terminal
    console.log("Server running at http://127.0.0.1:8080/");


## Require Hello

hello.js

    exports.world = function() {
        console.log('Hello World');
    }


main.js

    var hello = require('./hello');
    hello.world();


execute:

    $ node main.js



## Parsing log file

my_parser.js

    // Load the fs (filesystem) module.
    var fs = require('fs');//

    // Read the contents of the file into memory.
    fs.readFile('example_log.txt', function (err, logData) {

        // If an error occurred, throwing it will
        // display the exception and kill our app.
        if (err) throw err;

        // logData is a Buffer, convert to string.
        var text = logData.toString();

        var results = {};

        // Break up the file into lines.
        var lines = text.split('\n');

        lines.forEach(function(line) {
            if ( line.length ) {
                var parts = line.split(' ');
                var letter = parts[1];
                var count = parseInt(parts[2]);

                if(!results[letter]) {
                    results[letter] = 0;
                }

                results[letter] += parseInt(count);
            }
        });

        console.log(results);       
    });

example_log.txt

    2013-08-09T13:50:33.166Z A 2
    2013-08-09T13:51:33.166Z B 1
    2013-08-09T13:52:33.166Z C 6
    2013-08-09T13:53:33.166Z B 8
    2013-08-09T13:54:33.166Z B 5

execute:

    $ node my_parser.js

output:

    $ { A: 2, B: 14, C: 6 }



## Parse Log File Object Oriented Version

parser.js

    // Parser constructor.
        var Parser = function() {
    };

    // Parses the specified text.
    Parser.prototype.parse = function(text) {

    var results = {};

    // Break up the file into lines.
    var lines = text.split('\n');

    lines.forEach(function(line) {
        if ( line.length ) {
            var parts = line.split(' ');
            var letter = parts[1];
            var count = parseInt(parts[2]);

            if(!results[letter]) {
                results[letter] = 0;
            }

            results[letter] += parseInt(count);
        }
    });

    return results;
    };

    // Export the Parser constructor from this module.
    module.exports = Parser;


my_parser_oo.js

    // Require my new parser.js file.
    var Parser = require('./parser');

    // Load the fs (filesystem) module.
    var fs = require('fs');

    // Read the contents of the file into memory.
    fs.readFile('example_log.txt', function (err, logData) {
        // If an error occurred, throwing it will
        // display the exception and kill our app.
        if (err) throw err;

        // logData is a Buffer, convert to string.
        var text = logData.toString();

        // Create an instance of the Parser object.
        var parser = new Parser();

        // Call the parse function.
        console.log(parser.parse(text));        
    });

execute:

    $ node my_parser_oo.js

output:

    $ { A: 2, B: 14, C: 6 }


## counter.js

    var http = require('http');

    var userCount = 0;
    http.createServer(function (request, response) {
        console.log('New connection');
        userCount++;

        response.writeHead(200, {'Content-Type': 'text/plain'});
        response.write('Hello!\n');
        response.write('We have had '+userCount+' visits!\n');
        response.end();
    }).listen(8081);

    console.log('Server started');

counter.js will double the count each time the browser is refreshed because in addition to accessing the server, the browser also makes a request for the favicon, which increments the counter too.


## Express - static-file-server.js

    var express = require('express'),
    app = express();
    app.use(express.static(__dirname + '/public'));
    app.listen(3000);

in document root, execute:

    $ mkdir public
    $ cd public
    $ vim test.html

in browser:

    http://site:3000/test.html


## Express - Hello World

    var express = require('express');
    var app = express();

    app.get('/', function(req, res){
        res.send('hello world');
    });

    app.listen(3000);


## Express - Hello World - Version 2

    var express = require('express');
    var app = express();

    app.get('/', function (req, res) {
        res.send('Hello World!');
    });

    var server = app.listen(3000, function () {
        var host = server.address().address;
        var port = server.address().port;
        console.log('Example app listening at http://%s:%s', host, port);
    });


## Express - Router

router.js

    var express = require('express');
    var app = express();

    // respond with "Hello World!" on the homepage
    app.get('/', function (req, res) {
        res.send('Hello World from router.js\n');
    });

    // curl http://127.0.0.1:3000/user?name=jr
    app.get('/user', function (req, res) {
        var username = req.query.name;
        if ( username != undefined && username.length > 0 ) {
            res.send('user req for: ' + req.query.name + '\n');
        } else {
            res.send('user name missing\n');
        }
    });

    // accept POST request on the homepage
    app.post('/', function (req, res) {
        res.send('Got a POST request. name=\n');
    })

    // accept PUT request at /user
    app.put('/user', function (req, res) {
        res.send('Got a PUT request at /user\n');
    })

    // accept DELETE request at /user
    app.delete('/user', function (req, res) {
        res.send('Got a DELETE request at /user\n');
    })

    // start server and listen on port 3000
    var server = app.listen(3000, function () {
        var host = server.address().address;
        var port = server.address().port;
        console.log('Example app listening at http://%s:%s', host, port);
    });

execute:

    $ curl http://127.0.0.1:3000/user?name=jr