JavaScript is the most widely-used language for adding dynamic behavior to web pages. The JavaScript community contributes to a collection of libraries that extend and ease its use. In this course, you will learn about jQuery, a JavaScript library that makes it easy to add dynamic behavior to HTML elements.

Let’s look at an example of how JavaScript is used to add dynamic behavior to a web page (don’t worry about understanding the code).

const login = document.getElementById('login');
const loginMenu = document.getElementById('loginMenu');

login.addEventListener('click', () => {
  if(loginMenu.style.display === 'none'){
    loginMenu.style.display = 'inline';
  } else {
    loginMenu.style.display = 'none';
  }
});

In this example, JavaScript is used to apply behavior to an HTML element with id login. The behavior allows a user to click a LOGIN button that toggles a login form.

The code below accomplishes the same behavior with jQuery.

$('#login').click(() => {
  $('#loginMenu').toggle()
});

In this example, the same toggle functionality is accomplished using just three lines of code.