| Underlying Platform | Type | Responsibility | # of files in a program | Libraries | Etc | |
|---|---|---|---|---|---|---|
| Server-side (Node.js) | Operating system | Standalone program; Built-in web server module and other modules |
General purpose programming; Event-driven programming; To access server-side resources |
Usually several | Required or imported from other modules(, i.e., files) | Variables must be declared with let, var, and const. |
| Client-side | Web browser | A part of a web program | Event-driven programming; To access/manipulate HTML elements responding to events, such as mouse related and keyboard related events; To communicate with other programs running on other computers |
Usually one | Linked within <script> tag | Variables can be used without declaration with let, var, and const. |
http, https, cluster, fs, path, querystring, and url are very useful.| Type | Explanation | Keywords |
|---|---|---|
| CommonJS modules | Default in Node.js; Developped before ES modules | exports ..., require(...) |
| ECMAScript (ES) modules | JavaScript standard modules | export [default] ..., import ... from |
hello1.js as a module. (Note that each JS file is a module.) We can export multiple functions.
// hello1.js
exports.hello = function() {
console.log('Hello World!');
}
// main1.js
const helloooo = require('./hello1'); // Not hello1.js?
// When there is no file extension, .js is assumed.
// Obviously you can also use a full filename, even with a different file extension.
// require() returns an object having the property in 'exports' object from './hello1.js'.
helloooo.hello();
//-- at server ----------------------------------------
$ node main1.js
nano or vi on PuTTY terminal; or editing with WinSCP and execute commands on Command Terminal with WinSCP;
or editing with WinSCP and executing commands on PuTTY terminal.
Note that there is a button on WinSCP to open PuTTY terminal.
hello2.js as a module in a different way.
A module is exported as a function.
// hello2.js
module.exports = function() {
console.log('Hello World!');
}
// main2.js
const helloooo = require('./hello2');
helloooo();
//-- at server ----------------------------------------
$ node main2.js
const helloooo = require('./hello2'); // ./hello2.js or ./hello2/index.js
hello2.sjs and main2.sjs.
You can try with the above example.
| Default file extension | Examples | ||
|---|---|---|---|
| CommonJS modules with require/exports | .js | See the examples in Trial 1 and 2. | |
| ES modules with import/export | .mjs (or .js with package.json that includes "type":"module") |
// test_export.mjs
let age = 20;
let name = 'John';
const print = () => { return `${name}'s age is ${age}.`; }
export {age, name, print};
// test_import.mjs
import {print} from "./test_export.mjs";
console.log(print());
|
$ sudo apt-get update $ sudo apt-get install nodejs $ sudo apt-get install npm
https://nodejs.org/en/download/
npm is a Node.js package manager.
It is used to install other Node.js modules.$ npm install http-server
http module?hello.js - to print 'Hello World' on a console
// hello.js
console.log('Hello World!');
//-- at server ----------------------------------------
$ node hello.js
hello.js with your port number, not 8080, and run it.
hello_http.js - to print 'Hello World' from a web browser using the port number 8080
// hello_http.js
const http = require('http'); // Require 'http' module; We will study it in detail in the next section.
const server = http.createServer((req, res) => { // HTTP server object to deal with HTTP requests from clients
res.writeHead(200); // Sends the head to the client with the reponse number 200
res.end('Hello World!'); // Sends the message back to the client
});
server.listen(8080); // The server listens to the port number 8080.
//-- at server ----------------------------------------
$ node hello_http.js
//-- from a browser on a client -----------------------------------------
http://cs.tru.ca:8080
// Browsers usually try to use https, not http, and the above URL may not be reachable.
// You can try to use 198.162.21.132 instead of cs.tru.ca.
hello_http.js with your port number, not 8080, and run it.
index.html assumed? What is happening here?