Install Node.js from here
Create a new file, HelloWorld.js, add the following content.
console.log("HELLO WORLD");
You can see the output of your code by doing the following
node HelloWorld.js
Going forward we will execute each of our program the above way
A simple addition problem
Accept summation items as parameters for code. Before you consume them, check to see, if user has passed needed parameters. If not, error or return
// check for arguments passed to program
var hasArguments = function(array) {
if(array.length > 2) {
return true;
}
return false;
};
var isInteger = function(x) {
return Math.floor(x) === x;
}
var isFloat = function(x) {
return !!(x % 1);
}
// Get numbers from parameters
var numberFromVariable = function(param) {
if(isFloat(param)) {
return parseFloat(param);
}
return parseInt(param);
}
var sumOfIntegerArguments = function(array) {
var grandTotal = 0.0;
// start from index 2, proceed all the way to end
for(var index=2;index
Folder Explorer
This is to filter files in a folder. We could achieve this in 2 ways. We could either put all things in file or export part of a functionality to another file. This way, we could keep the code cleanMethod 1 (All in one file)
var fs = require('fs'),
path = require('path');
var directoryLocation;
var filter;
var listDirectoryCallback = function(err, files) {
for(var index =0;index 3) {
filter = process.argv[3];
// check for '.', if there is one, rmeove it
if(filter[0] != '.') {
filter = '.' + filter;
}
}
checkAndListFolder(directoryLocation, fileStatsCallback);
})();
Method 2 (Exports logic)
By exporting certain functions into another file, we make it easier on the programs from readability perspective as well as from reusabilityFolderExplorerMain.js
var checkAndListFolder = require('./FolderExplorer');
var listDirectoryFailed = function() {
console.log('ERROR: This is not a directory. Please pass on directory name to explore')
};
var listDirectoryCallback = function(err, files) {
if(err) {
console.log('ERROR: undefined');
listDirectoryFailed();
}
for(var index =0;index 3) {
checkAndListFolder(process.argv[2], process.argv[3], listDirectoryCallback);
}
FolderExplorer.js
var fs = require('fs'),
path = require('path');
var checkAndListFolder = function(directoryLocation, filter, callback) {
fs.readdir(directoryLocation, function(err, files) {
if(err) {
return callback(err);
}
var fileList = [];
fileList = files.filter(function(file) {
return path.extname(file) === '.' + filter;
});
callback(null, fileList);
});
};
module.exports = checkAndListFolder;
A simple HTTP Server
A very simple, basic HTTP server that would listen on a port passed on as argument or on 1337
var http = require('http');
var port = process.env.PORT || 1337;
var server = http.createServer(function(request, response) {
response.setHeader('Content-Type', 'text/plain');
response.end('Hello World!!!');
});
server.listen(port, function() {
console.log('Listening in port ' + port);
});
A simple HTTP client
var http = require('http');
if(process.argv.length <= 2) {
console.log('ERROR: Please pass the URL to read');
return;
}
var URL = process.argv[2];
//'http://localhost:1337/'
http.get(URL, (res) => {
// console.log('GET response: ' + res.statusCode);
res.on('error', (err) => {
console.log('Error :' + err);
});
res.on('data', (data) => {
console.log(data.toString());
});
res.on('end', () => {
//console.log('END of data');
});
res.resume();
});
A simple HTTP client that streams data
var http = require('http');
if(process.argv.length <= 2) {
console.log('ERROR: Please pass the URL to read');
return;
}
var URL = process.argv[2];
http.get(URL, (res) => {
var streamData = "";
res.on('error', (err) => {
console.log('Error :' + err);
});
res.on('data', (data) => {
if(streamData.length <= 0) {
streamData = data.toString();
} else {
streamData += data.toString();
}
});
res.on('end', () => {
console.log('' + streamData.length);
console.log(streamData);
});
res.resume();
});
Another way of achieving streaming HTTP client
var http = require('http');
var bl = require('bl')
if(process.argv.length <= 2) {
console.log('ERROR: Please pass the URL to read');
return;
}
var URL = process.argv[2];
http.get(URL, (res) => {
var streamData = "";
res.pipe(bl(function(err, data) {
if(err) {
console.log('ERROR: ' + error);
} else {
var finalData = data.toString();
console.log(finalData.length);
console.log(finalData);
}
}));
});
A simple GET request
Do a simple GTE request from either a browser or cUrl command to see if this program handles GET request the way it should.
/**
* Created by krishnan on 2/21/16.
*/
var http = require('http');
var url = require('url');
var Router = require('router');
var finalhandler = require('finalhandler');
var port = Number(process.argv[2]) || 8080;
var server = http.createServer(function(req, res) {
router(req, res, finalhandler(req, res))
});
var router = Router();
router.route('/').get(function(req, res) {
res.setHeader('Content-Type', 'text/plain; charset=utf-8');
res.end('Default route - Reach out to /api/parsetime for time information.');
});
router.route('/api/parsetime').get(function(req, res) {
var queryData = url.parse(req.url, true).query;
res.setHeader('Content-Type', 'text/plain; charset=utf-8');
if(queryData.iso == null) {
res.end("ISO parameter is NULL");
} else {
//res.write("ISO is: " + queryData.iso + "\n");
var date = new Date(queryData.iso);
//res.write("New date is: " + date);
var stringDate = "{hour: " + date.getHours() + ", minute: " + date.getMinutes() + ", second: " + date.getSeconds() + "}";
var jsonDate = JSON.stringify(eval("(" + stringDate + ")"));
res.end(jsonDate);
}
});
router.route('/api/unixtime').get(function(req, res) {
var queryData = url.parse(req.url, true).query;
res.setHeader('Content-Type', 'text/plain; charset=utf-8');
if(queryData.iso == null) {
res.end("ISO parameter is NULL");
} else {
//res.write("ISO is: " + queryData.iso + "\n");
var date = new Date(queryData.iso);
//res.write("New date is: " + date);
var stringDate = "{unixtime:" + date.getTime() + "}";
var jsonDate = JSON.stringify(eval("(" + stringDate + ")"));
res.end(jsonDate);
}
});
server.listen(port, function() {
console.log('Listening on port: ' + port);
});
A simple POST request
We can make a simple POST request using cUrl to see if this code processes POST command as well as it should
var http = require('http');
var port = Number(process.argv[2]);
var server = http.createServer(function(req, res) {
res.setHeader('Content-Type', 'text/plain');
if(req.method === "POST") {
var reqMessage = "";
req.on('data', function(buffer) {
reqMessage += buffer.toString();
});
req.on('end', function() {
// console.log('User put in: ' + reqMessage);
res.end(reqMessage.toUpperCase());
});
}
});
server.listen(port, function() {
// console.log('Server listening in port ' + port);
})
A simple Socket server
A simple socket server that you can connect using 'nc' command, to see if you can connect and see things work.
var net = require('net');
var now = function() {
var connectionTime = new Date();
var dd = (connectionTime.getDate() < 10 ? '0' : '') + connectionTime.getDate();
var mm = ((connectionTime.getMonth() + 1) < 10 ? '0' : '') + (connectionTime.getMonth() + 1);
return connectionTime.getFullYear() + "-" + mm + "-" + dd + " " + connectionTime.getHours() + ":" + connectionTime.getMinutes();
}
var server = net.createServer();
if(process.argv.length <= 2) {
console.log("ERROR: Please pass the port to listen to");
return;
}
PORT = Number(process.argv[2]);
if(PORT <= 80) {
console.log("ERROR: Invalid port number");
return;
}
server.on('connection', function(conn) {
var connectionTime = new Date();
var dd = (connectionTime.getDate() < 10 ? '0' : '') + connectionTime.getDate();
var mm = ((connectionTime.getMonth() + 1) < 10 ? '0' : '') + (connectionTime.getMonth() + 1);
console.log(connectionTime.getFullYear() + "-" + mm + "-" + dd + " " + connectionTime.getHours() + ":" + connectionTime.getMinutes());
conn.setEncoding('utf8');
conn.on('close', function() {
console.log('Connection closed');
});
conn.on('data', function(buffer) {
process.stdout.write('Server received data: ' + buffer);
});
/*// var emit = conn.emit;
// conn.emit = function(event) {
// console.log('Connection emitted event: %j', event);
// emit.apply(conn, arguments);
// };*/
});
server.listen(PORT, function() {
console.log('Server listening at port: %j', server.address());
});
