Matching tags with regular expressions

[Reto]

With forEachTidler I am trying to find tiddlers with tags matching
certain patterns. I read carefully through the posts in this group
related to this topic but wasn't able to figure out a solution.

This is what I have:

<<forEachTiddler where
'tiddler.tags.sort().join("]]").contains(new RegExp("....\-..
\-..","gm"))'
>>

Date tags with format "YYYY-0MM-0DD" should be found. As far as I
understood the tag array is converted to a string after the join but I
obviously do not understand how to apply the RegExp function to it ...

Any hints welcome!

[Eric Shulman]

> <<forEachTiddler where
> 'tiddler.tags.sort().join("]]").contains(new RegExp("....\-..
> \-..","gm"))'
>
> Date tags with format "YYYY-0MM-0DD" should be found. As far as I
> understood the tag array is converted to a string after the join but I
> obviously do not understand how to apply the RegExp function to it ...

To test a text string against a regular expression, you can use
the .match() method of the string, passing the regexp as an argument:

var foo="some text";
if (foo.match(/some regexp/)) { ... }

If the pattern is found within the string, match() returns an *array*,
where match[0] is the complete matched text, and match[1..n] contain
matches for parenthesized sub-expressions (if any were used in the
regexp). If no match is found, then match() returns a NULL (==false)
value.

Try this:

<<forEachTiddler where
'tiddler.tags.join(" ").match(/[0-9]{4}-[0-9]{2}-[0-9]{2}/)'

* I used a literal regexp (/.../) instead of creating a new RegExp
object within the forEachTiddler loop (more efficient).
* The regexp uses more specific matching (looks for numerics only)
* Except within the "[0-9]" regexp syntax, "-" is treated literally
and is not a special symbol. It doesn't need backslash-quoting to be
matched.
* The tags don't need to be sorted, since you are matching across the
whole set of tags at once
* The tags are joined with " " rather than "]]".

enjoy,
-e
Eric Shulman
TiddlyTools / ELS Design Studios

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[Reto]

Works like a charm, muchas gracias! And thanks for the helpfull
coments.

Cheers
Reto

[Reto]

Any idea how to avoid the NULL respectively replace it by an empty string if match doesn't get any result?

tiddler.tags.join(" ").match(/[0-9]{4}-[0-9]{2}-[0-9]{2}/).replace(/\0/g,"")

ends up with "TypeError: Cannot  call method 'replace' of null".

[Eric Shulman]

> Any idea how to avoid the NULL respectively replace it by an empty string
> if match doesn't get any result?
>
> tiddler.tags.join(" ").match(/[0-9]{4}-[0-9]{2}-[0-9]{2}/).replace(/\0/g,"")

Use this:

tiddler.tags.join(" ").match(/[0-9]{4}-[0-9]{2}-[0-9]{2}/)||""

-e

[Reto]

Yes, that's it. Thanks!

Reto