JavaScript was initially created to “make web pages alive”.

The programs in this language are called scripts. They can be written right in a web page’s HTML and run automatically as the page loads.

When JavaScript was created, it initially had another name: “LiveScript”. But Java was very popular at that time, so it was decided that positioning a new language as a “younger brother” of Java would help.

What can JavaScript do?

For instance, in-browser JavaScript is able to:

• Add new HTML to the page, change the existing content, and modify styles.
• React to user actions, run on mouse clicks, pointer movements, and key presses.
• Send requests over the network to remote servers, download and upload files (so-called AJAX and COMET technologies).
• Get and set cookies, ask questions to the visitor, and show messages.
• Remember the data on the client-side (“local storage”).