What's the difference between JavaScript and JScript?

Question

Just different names for what is really ECMAScript. John Resig has a good explanation.

Here's the full version breakdown:

• IE 6-7 support JScript 5 (which is equivalent to ECMAScript 3, JavaScript 1.5)
• IE 8 supports JScript 6 (which is equivalent to ECMAScript 3, JavaScript 1.5 - more bug fixes over JScript 5)
• Firefox 1.0 supports JavaScript 1.5 (ECMAScript 3 equivalent)
• Firefox 1.5 supports JavaScript 1.6 (1.5 + Array Extras + E4X + misc.)
• Firefox 2.0 supports JavaScript 1.7 (1.6 + Generator + Iterators + let + misc.)
• Firefox 3.0 supports JavaScript 1.8 (1.7 + Generator Expressions + Expression Closures + misc.)
• The next version of Firefox will support JavaScript 1.9 (1.8 + To be determined)
• Opera supports a language that is equivalent to ECMAScript 3 + Getters and Setters + misc.
• Safari supports a language that is equivalent to ECMAScript 3 + Getters and Setters + misc.

As far as I can tell, two things:

1. ActiveXObject constructor
2. The idiom f(x) = y, which is roughly equivalent to f[x] = y.

From Wikipedia: http://en.wikipedia.org/wiki/Jscript

JScript is the Microsoft dialect of the ECMAScript scripting language specification.

JavaScript (the Netscape/Mozilla implementation of the ECMA specification), JScript, and ECMAScript are very similar languages. In fact the name "JavaScript" is often used to refer to ECMAScript or JScript.

Microsoft uses the name JScript for its implementation to avoid trademark issues (JavaScript is a trademark of Oracle Corporation).

JScript is Microsoft's implementation of the ECMAScript specification. JavaScript is the Mozilla implementation of the specification.

Javascript, the language, came first, from Netscape.

Microsoft reverse engineered Javascript and called it JScript to avoid trademark issues with Sun. (Netscape and Sun were partnered up at the time, so this was less of an issue)

The languages are identical, both are dialects of ECMA script, the after-the-fact standard.

Although the languages are identical, since JScript runs in Internet Explorer, it has access to different objects exposed by the browser (such as ActiveXObject)