Fossil

# Use of JavaScript in Fossil

## Philosophy & Policy

The Fossil development project’s policy is to use JavaScript where it
helps make its web UI better, but to offer graceful fallbacks wherever
practical. The intent is that the UI be usable with JavaScript entirely
disabled. In every place where Fossil uses JavaScript, it is an
enhancement to provided functionality, and there is always another way
to accomplish a given end without using JavaScript.
practical. The intent is that the UI be usable with JavaScript
entirely disabled. In almost all places where Fossil uses JavaScript,
it is an enhancement to provided functionality, and there is always
another way to accomplish a given end without using JavaScript.

This is not to say that Fossil’s fall-backs for such cases are always as
elegant and functional as a no-JS purist might wish. That is simply
because [the vast majority of web users run with JavaScript enabled](#stats),
and a minority of those run with some kind of [conditional JavaScript
blocking](#block) in place. Fossil’s active developers do not deviate from that
norm enough that we have many no-JS purists among us, so the no-JS case

    The Fossil project’s developers aim to remain compatible with
    the largest portions of the client-side browser base. We use only
    standards-defined JavaScript features which are known to work in the
    overwhelmingly vast majority of browsers going back approximately 5
    years, at minimum, as documented by [Can I Use...?][ciu] We avoid use of
    features added to the language more recently or those which are still in
    flux in standards committees
    flux in standards committees.

    We set this threshold based on the amount of time it typically takes for
    new standards to propagate through the installed base.

    As of this writing, this means we are only using features defined in
    [ECMAScript 2015][es2015], colloquially called “JavaScript 6.” That is a
    sufficiently rich standard that it more than suffices for our purposes.

`/fileedit` implementation. It would have all of the same downsides as
the old wiki editor: the users would lose their place on each save, they
would have no local backup if something crashes, etc. Still, we are
likely to accept such a [contribution][cg] as long as it doesn’t
interfere with the new editor.

[edoc]:  /doc/trunk/www/embeddeddoc.wiki
[fedit]: /help?cmd=/fileedit
[fedit]: /doc/trunk/www/fileedit-page.md


### <a id="ln"></a>Line Numbering

When viewing source files, Fossil offers to show line numbers in some
cases. ([Example][mainc].) Toggling them on and off is currently handled
in JavaScript, rather than forcing a page-reload via a button click.