What is jQuery?

jQuery is an open source JavaScript library or module, which basically means that it is a JavaScript file that has been written by someone else to make our tasks concise and easy. jQuery was made to make HTML—JavaScript interaction easier, it has a lot of stuff related to event handling and animations built in.

It is not a new programming language; it is just a set of functions and properties written in JavaScript.

Why jQuery?

• jQuery is cross-browser compatible. This means that when you run your code, the output will remain the same, independent of the browser. It won't change from one browser to another.
• jQuery has a shorter "syntax" than JavaScr...

In this tutorial you'll learn about a special type of functions — callbacks.

We will also look at pre-loading static assets like scripts, images and stylesheets into the browsers cache so that they can be instantly fetched from the cache which is a lot faster than downloading from a remote URL.

Let's get started!

Set-up for this tutorial

For this tutorial, to ensure that everyone sees similar results and is able to run the code properly, we will change some settings in Google Chrome.

Open up the console using Ctrl + Shift + J. In the top bar there is a tab called Network. Click on it. You should see:

In this tutorial we will learn about two built-in utilities of JavaScript — the Math module and the Date module.

Math

The Math module has functions to do various mathematical operations, and it also includes functions for generating random numbers. It has many constant values as well, like the value of pi (ratio of a circle's circumference to its diameter), etc.

Math Constants

Let's start by looking at some of the constants defined in the Math object. We will use the JavaScript Console for this tutorial to run the examples interactively.

Math.E is the Euler's constant — e. It is used as th...

HTML Forms are used everywhere on web - for creating an account, for submitting applications, for submitting payment information, etc. In this tutorial you will learn how to read HTML form data from JavaScript and how to perform form validation (that the user has filled the form as expected).

Note: Once the form has been filled satisfactorily by the user and submitted, often the information is sent to server (the computer which responds to user requests for your website) or stored in your database. For example, if the user just entered his log-in details, this data is sent to the server, which responds back saying whether the log-in credentials were correct or not. We'll cover such interactions (making web-requests from JavaScript) later in the course.

HTML Forms

An HTML form is defined by the <form> and <...