JavaScript gives HTML designers a programming tool—HTML authors are normally not programmers, but JavaScript is a scripting language with a very simple syntax!
JavaScript can put dynamic text into an HTML page—A JavaScript statement like this:
document.write( "<h1>" + name + "</h1>" )
can write a variable text into an HTML page.
JavaScript can react to events—A JavaScript can be set to execute when something happens, like when a page has finished loading or when a user clicks on an HTML element.
JavaScript can read and write HTML elements—A JavaScript can read and change the content of an HTML element.
JavaScript can be used to validate data—A JavaScript can be used to validate form data before it is submitted to a server.
JavaScript can be used to detect the visitor’s browser—A JavaScript can be used to detect the visitor’s browser, and—depending on the browser—load another page specifically designed for that browser.
JavaScript can be used to create cookies—A JavaScript can be used to store and retrieve information on the visitor’s computer.
JavaScript = ECMAScript
JavaScript is an implementation of the ECMAScript language standard (ECMA-262).
JavaScript was invented by Brendan Eich at Netscape, and has appeared in all browsers since 1996.
The official standardization was adopted by the ECMA organization (an industry standardization association) in 1997.
The ECMA-262 was approved as an international ISO (ISO/IEC 16262) standard in 1998.
The development is still in progress.
Demonstration
The following demonstration shows how the script of HTML and JavaScript is displayed on the Web.