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JavaScript in Opera, general information

JavaScript is a scripting language that was introduced to enhance Web site interaction. ECMAScript is an international standard for JavaScript.

JavaScript and Java

JavaScript and Java, though easily confused because of similar names, are actually very different languages. Java is a programming language developed by Sun Microsystems, while JavaScript is a scripting language that was introduced by Netscape. Opera 3 and above supports JavaScript by following the ECMAScript standard. Therefore, your Opera installation supports JavaScript whether or not you have chosen to download Java.

Enabling and disabling JavaScript

Opera supports JavaScript, but you can choose whether or not to enable it. The negative consequences of disabling JavaScript depends on the sites you visit. Some use JavaScript purely for visual effects, but it is very common that JavaScript is used to create navigation menus and similar, and therefore, JavaScript is an important part of the Web today.

The pitfalls of browser detection

Some webmasters write their site with certain browsers and versions in mind, and one of the ways JavaScript is being used is for browser detection: to check if you are using their target browser. If you have ever received a message saying that you need to upgrade your browser to display the Web page, you've most likely run into a browser detection script. The problem is that Opera in fact is capable of displaying most of the Web sites. For tips about what to do in this situation, see Opera and Browser Detection.

The ECMA-262 standard

ECMA is an international industry association founded in 1961 and dedicated to the standardization of information and communication systems. Opera's JavaScript implementation follows the ECMAScript standard.

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