What is Javascript?

Javascript is a programming language. Javascript was engineered at Sun Microsystems with the intention of creating a method of manipulating webpages on a user's computer, without the need for refreshing the page. The first web browser that supported JavaScript was Netscape 2.0B3. Internet Explorer has never supported valid Javascript, instead supporting a Microsoft version called JScript. JScript is over 99% compatible with Javascript, such that most people do not realize that it is not Javascript. The few compatibility issues that do arise are usually attributed to the fact that Microsoft products traditionally fall short of standards compliance.

While Javascript is often used to enhance the browsing experience, several annoyances are commonly associated with the technology. Popup messages and image rollovers are two such annoyances. Also, some security issues have arisen in early implementations, leading people to disable or limit Javascript support in their web browsers. However, some websites do require the use of Javascript. This is usually considered bad practice, however, and in recent years the number of such sites has been declining. Of particular note is the tendency for banking websites to rely on Javascript for security purposes. As Javascript is run client-side, this security model is very easily bypassed. Websites that rely on Javascript for security purposes are dangerous and should be avoided.

Another technology with a similar name, Java, is not related in any way with Javascript. Java is often confused with Javascript as Java applets are commonly embedded in webpages, and Javascript is a programming language designed to manipulate webpages. Also, the similar names cause understandable confusion. Both are products of Sun Microsystems.