CSCI 121 - Lecture 9 - Introduction to JavaScript

Topics Covered

1. History
• It is NOT java.
• Developed in 10 days in 1995 by Brendan Eich of Netscape.
• "Necessity is the mother of invention" - a client-side scripting language was needed.
• Needed a way for a user to interact with a web page and trigger scripts that would cause page updates, etc.
• Great history here: http://www.2ality.com/2011/03/javascript-how-it-all-began.html.
• Adopted as a standard in 1996, 1997 by ECMA, with ECMAScript the name of the official standard.
• Competing client-side scripting alternatives existed until 2005 and were all but phased out by 2008 when most alternatives died off.
• Web 2.0 paradigm of development, Ajax as a standard, jquery and other libraries, HTML5 have lead to JavaScript as becoming a vital technology in the Internet Programming toolbox today.
2. Adding JavaScript to a web page
• The <script> tag is used to define client-side script (JavaScript) within an HTML document (web page).
• The <script> element may contain either JavaScript code or it may point to a script file through its src attribute.
3. Writing content to a web page dynamically
• JavaScript may write to a web page in several ways.
• The most rudimentary way is to use the document.write function of the Document Object Model (DOM).
• When called as the page is loaded, document.write appends.
• Beware: If called after the page is loaded document.write replaces all the page content.