I think there's much confusion among developers when it comes to define what jQuery really is. Point one: jQuery is not a web standard. Point two: jQuery works better when a web browser features a better support of the ECMAScript, JavaScript and DOM standards. Browsers should support web standards first. Any other kind of enhancement is greatly appreciated but not required.
If you take a look at the Internet Explorer 10 Guide for Developers , there is no mention of jQuery. Does this mean that jQuery doesn't work in IE 10? Absolutely not.
Reading the meaningful introduction to JavaScript by Mozilla is also interesting:
JavaScript (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB.
The JavaScript standard is ECMAScript. As of 2012, all modern browsers fully support ECMAScript 5.1. Older browsers support at least ECMAScript 3. A 6th major revision of the standard is in the works. The current progress of different new and improved features can be followed on the dedicated wiki.
This section of the site is dedicated to the JavaScript language itself, the parts that are not specific to Web pages, or other host environments. For information about APIs specific to Web pages, please see DOM. Read more about how DOM and JavaScript fit together in the DOM Reference.
Does this mean that jQuery doesn't work in Firefox only because it's only mentioned in the Related topics? Absolutely not. Neither the Chrome official reference mentions jQuery, but we all know that jQuery works very well in Chrome.
jQuery is written in JavaScript. The problem is that many developers jump directly to write jQuery code without having a strong knowledge of JavaScript. This approach leads many people to think that jQuery is just another programming language or, to some extent, another web standard.
Well, this is not the case. jQuery works because the underlying support of a web browser to web standards works as it should. Since jQuery is not a web standard nor a programming language but just a JavaScript library, web browsers cannot say "yes, we support jQuery".
It's jQuery that supports a specific browser, not the contrary.