This has not stopped individual vendors from adding their own tweaks to the specifications. Care must be taken to avoid these if you are seeking cross browser compatibility
- You cannot write standalone applications with it, and mainly for web security reasons, it has very limited capability for reading or writing files.
- Pre processing of web based forms. Before sending a web based form to a server, the contents can be checked, to make sure the data is valid. All this processing takes place on the client machine.
- Accessing Cascading Style sheets and their properties. For example hiding or revealing the contents of a <DIV> by changing the display style property.
- To add dynamic content to web pages by interacting with a users actions (or events), for example with drop down menu's, or animation.
Events are triggered irrespective of whether there is a corresponding event handler or not. If there is no event handler, and corresponding function to deal with it, then the event is ignored.
That is a qualified yes, provided the browser in question follows both W3C and ECMA specifications. As noted above, Microsoft Explorer is not ECMA compliant, so code that will run on other browsers will not work without modification.
Even if the browser is compliant, the vendor may be slow in implementing new features, so again differences arise between the browsers. This is a moving target which the site quirsksmode.org monitors Popular browsers are tested against specification features, but they only answer to this problem is to run your scripts in the various browsers and see.