Skip to content

Latest commit

 

History

History
189 lines (128 loc) · 6.21 KB

nodejs.md

File metadata and controls

189 lines (128 loc) · 6.21 KB

node.js

node.js can be downloaded from the node.js website for Windows, macOS, Linux and other platforms. If you wish to use this resource, you will need to download it.

Having a understanding of javascript programming concepts will be beneficial.

What is it?

As found on the node.js About page:

As an asynchronous event driven JavaScript runtime, Node is designed to build scalable network applications. Upon each connection the callback is fired, but if there is no work to be done, Node will sleep.

node.js is designed to be a server run package which takes advantage of the javascript syntax. node.js makes use of modules to help, build, and create web development, server-side components and compilers to name a few.

Depending on the depth you wish to use node.js, their API Documentation will be a great asset.

Who is using node.js?

  • Netflix
  • Uber
  • Paypal
  • eBay

Activity

node.js can run through a packaged node.exe file which is a command line shell that can run javascript.

What appears when you run the following blocks of code through node.exe?

5

var x = 5 then call x

x*3

for (var i = 0; i<10; i++) { console.log(i); }

var d = new Date() then call d

Now try and run code just looks for elements such as:

document.getElementbyId('h1')

What happened and why did it happen? node.exe is essentially javascript without the browser operations. There is no document (HTML) for node.js to target to retrieve this information.

Running in Terminal

When running node.js through a Command Line or Terminal, you can access applications you have written and saved as javascript.

This can be done by locating the folder which contains for .js file and using a node prefix when typing into Command line.

Example

node app.js or simply node app.

Be sure when running .js files, you have accessed the necessary root directory through the command line where the file is located.

Directory finding

Use cd at the start of your command then folder name. You have to been in a root directory of that folder to access it. To see what folders and files are in the current directory, use ls in the command line.

If your folder contains spaces:

  • for Windows use cd "folder name" to make sure command line reads the space.
  • for Mac use cd folder\ name to make sure command line reads the space.

Activity

Copy the below code and save it as to your computer to run through Command Line.

app1.js

console.log('Hello World');

This should return the string in Command Line.

You can also run javascript functions through this method.

app2.js

function greeting(greet) {
  console.log(greet);
}

greeting('Hello again World');

The whole function should be run then returned.

Setting up a local server

NPM - node.js Package Manager is used to install node.js modules.

package.json - This is important. This is created by running npm init in Command Line. It will should be placed in the root of your application so NPM knows how the application is structured. When running npm init, you are going to be prompted to enter some information. As an example the first one to show up is name with a name in brackets beside it. This name in brackets is a default name and all the titles will have a default or no input. To select the default or leave blank, just press enter.

These areas fields are: name, version, description, entry point, test command, git repository, keywords, author, license

entry point would be most important one to get correct. This is the main file that package.json connects with. This is generally a .js file.

Once completed, this information will published into a package.json file.

If npm init does not run you may need to try sudo npm init instead.

Using ES2015 (or ES6) Syntax, we can create a local server. Using a few modules from within the node.js package, we can set this up very simply.

More information about ES2015/ES6 can be found here and here explaining ES2015 Syntax.

app3.js

// node module 'require' (core)
const http = require('http');

// loop address
const hostname = '127.0.0.1';

const port = 3000;

// request and response
const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-type', 'text/plain');
  res.end('Hello World yet again');
});

server.listen(port, hostname, () => {
  console.log('Server started on port '+port);
});

Once this has been run on Command Line, go to http://127.0.0.1:3000 and see what happens.

If done correctly, this is the result of setting up a simple local server on your computer.

In this example fs (file system) has been added. This is used your accessing files.

Copy both app4.js and index.html for this exercise make sure they are in the same folder.

app4.js

// node module 'require' (core)
const http = require('http');

// file system module
const fs = require('fs');

// loop address
const hostname = '127.0.0.1';

const port = 3000;

fs.readFile('index.html', (err, html) => {
  if (err) {
    throw err;
  }

  // request and response
  const server = http.createServer((req, res) => {
    res.statusCode = 200;

    res.setHeader('Content-type', 'text/plain');
    res.write(html);
    res.end();
  });

  server.listen(port, hostname, () => {
    console.log('Server started on port '+port);
  });

});

index.html

<!DOCTYPE html>
<html>
  <head>
    <title>Test HTML</title>
  </head>
  <body>
    <h1>Guess What?</h1>
    <h2>It's me, 'Hello World'</h2>
  </body>
</html>

Once loaded, have a look at how the webpage looks. Why is that?

What if you changed res.setHeader('Content-type', 'text/plain') to res.setHeader('Content-type', 'text/html')?

Restart your server through Command Line (Ctrl + C and run the app again), and reload your webpage ( http://127.0.0.1:3000 ). Has it changed?