Asynchronous JavaScript

This project is a demonstration of asynchronous JavaScript on the server (using NodeJS) and in the browser.

Requirements

• git
• NodeJS

Get the Code

Download the code for this project by using git clone:

git clone https://github.com/Learn-by-doing/async-javascript.git

Install Node Modules

Like any node project, you will need to run download and install the required node modules for the project to run. Use the following command:

npm install

Once that has finished, you can run the program like this:

npm start

You should see the following if everything is OK:

Server started and listening at localhost:3000

Try the demo

Open your browser to localhost:3000 and enter a search query. After a short while you should see search results in the page. Here is what is happening:

• The browser:
  • intercepts the search form submission.
  • sends a request to your local web server.
  • waits for a response from the local web server.
• The local web server:
  • receives the request.
  • sends a request to the Shodan web API.
  • waits for the response from Shodan.
  • receives the response from Shodan.
  • sends a response to the browser.
• The browser receives the response from the local web server.

Each of these requests/responses are asynchronous and allow other operations to happen during the waiting time.

Going further

The JavaScript code running in the browser can be found in the index.html file. There are four different examples of asynchronous JavaScript in the browser-side code:

• A simple timeout loop
• A timeout with a delay of 0 seconds
• An AJAX request
• Use of the async.util function from the async.js utility library.

Read the source and comments for further explanation.