# Node.js code snippets

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 #nodejs - #programming - #javascript


[[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


## Post URI 

    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://127.0.0.1:3000/4/site-info
    // or
    // curl http://127.0.0.1:3000/post/site-info
    app.get('/post/:title', function (req, res) {
        var article = req.param('title');
        if ( article != undefined && article.length > 0 ) {
            if ( isNaN(article) ) {
                // uri after post equals article title
                res.send('article title : ' + article + '\n');
            } else {
                // uri after post equals a number
                res.send('article id : ' + article + '\n');
            }
        } else {
            res.send('article request missing\n');
        }
    });


## HTTP-Get

    var api_posts_url = 'http://toledowinter.com/api/v1/posts/site-info';

    http = require('http');

    http.get(api_posts_url, function(res) {
        console.log("Got response: " + res.statusCode);
        // console.dir(res);

        res.on("data", function(chunk) {
            console.log("BODY: " + chunk);
        });

    }).on('error', function(e) {
        console.log("Got error: " + e.message);
    });

    // 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);
    });


## Parse JSON

    var json = '{"result":true,"count":1}',
    obj = JSON.parse(json);
    console.log(obj.count);
    console.log(obj.result);


## For-In Loop

var p =
    {
        "p1": "value1",
        "p2": "value2",
        "p3": "value3"
    };

    for (var key in p) {
        if (p.hasOwnProperty(key)) {
            console.log(key + " -> " + p[key]);
        }
    }


## Different Version of GET

    http = require('http');

    var options = {
        host: 'toledowinter.com',
        port: 80,
        path: '/api/v1/posts/site-info'
    };

    http.get(options, function(res) {
        console.log("Got response: " + res.statusCode);
        res.on("data", function(chunk) {
            console.log("BODY: " + chunk);
            obj = JSON.parse(chunk);
            console.log("\n formatted created date: " + obj.formatted_created_date);

            for (var key in obj) {
                if (obj.hasOwnProperty(key)) {
                    console.log(key + " -> " + obj[key]);
                }
            }
        }); // close res.on
    }).on('error', function(e) {
        console.log("Got error: " + e.message);
    }); // close http.get


## Express-Handlebars

var express = require('express');
var exphbs  = require('express-handlebars');

var app = express();

// in directory: views/layouts/main.handlebars
app.engine('handlebars', exphbs({defaultLayout: 'main'}));
app.set('view engine', 'handlebars');

// in directory: views/home.handlebars
app.get('/', function (req, res) {
    res.render('home');
});

// in directory: views/simple.handlebars
app.get('/simple', function(req, res){
    var data = {name: 'Gorilla'};
    res.render('simple', data);
});

app.listen(3000);


views/home.handlebars

    <h1>Example App: Home</h1>

views/simple.handlebars

    <h1>{ {name}}</h1>

views/layouts/main.handlebars

    <!DOCTYPE html>
    <html>
    <head>
    <meta charset="utf-8">
    <title>Example App</title>
    </head>
    <body>
        { { {body}}}
    </body>
    </html>


## Basic HTTP Request with Native Node.js

    function getTestPersonaLoginCredentials(callback) {
        return http.get({
            host: 'personatestuser.org',
            path: '/email'
        }, function(response) {
            // Continuously update stream with data
            var body = '';
            response.on('data', function(d) {
                body += d;
            });
            response.on('end', function() {
                // Data reception is done, do whatever with it!
                var parsed = JSON.parse(body);
                callback({
                    email: parsed.email,
                    password: parsed.pass
                });
            });
        });
    },