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Javascript® vs. JScript®
Javascript® is a registered trademark of Netscape Communications Corporation. JScript® is a registered trademark of Microsoft Corporation.
Although the languages are quite similar, the primary elements of the languages provide support in a different manner. If you are going to utilize the features of scripting within web pages it's necessary to become familiar with the nuances. The languages are specific to the browser's version and release as well as the platform where the web browser is running. With the most current web browser releases this issue is less significant as in previous releases. With the implementation of the DOM (Document Object Model) standard differences between the two language begin to dissolve to some extent. Bare in mind, however, the same design issues continue to be a consideration until the full implementation of the various W3C standards is achieved across all devices and platforms, and web browsers fully supporting those standards are in use by the majority of users.
One of the most significant issues persisting across platforms is the browser specific extension implementations. Extensions are proprietary functions beyond the scope of the standards and do not fall under the embrella of recommended standards. Today, these occur primarily within the scope of Microsoft Internet Explorer where numerous extensions have been implemented while at the same time the W3C standards are only partially implemented. This issue pertains to websites designing and developing to exploit capabilities of those browser specific extensions without supporting browsers that do not support those standards. The rationale behind this practice is that the supportive web browser is readily available for download. However, often this is not the case due to connection speeds or the device being used to access the website. The most common deployment error is forgetting the nuances across computer platforms. Clearly many of these browser specific extensions are unique to only one platform and are not available to users not running on that platform.
Bottom-line with regards to handling variations between JScript® and Javascript® is still most significant with respect to supporting older versions of web browsers. It is recommended that websites continue to support older browsers if the website's audience is the general public as opposed being a dedicated Intranet/Extranet environment where minimum browser requirements may be specifically enforced. Websites can state to its visitors that they must use version X, although a loss of potential business must be expected as there are still many users using old browsers even though newer versions are readily available as free distributions.
NOTE: Refer to W3C's (World Wide Web Consortium) "Intrinsics" (Chapter 18 - Scripts) in the most current HTML approved standard for aspects specific to web device/browser scripting as it pertains to HTML elements. (Javascript® is a registered trademark of Netscape Communications Corp.; JScript® is a registered trademark of Microsoft Corp.)