[Javascript] Re: RegExp question

[vallinis]

The original question was:

-------
I tried that, with... var pattern = new RegExp("/course_/(\d+)_\d+","ig"); 
...and... var pattern = new RegExp("/course_(\d+)_\d+/","ig"); ...neither 
seems to work.
-------

Actually, the problem is as follows:

initialize a new RegExp such as:
pattern = new RegExp()

this is now, obivously, a RegExp object. Therefore it can get avail of all 
the built in methods such as compile.
See this strange thing now:
if you have a FORM OBJECT VALUE and you pass it to a compile method as it 
may be held by a RegExp object like  our 'pattern', doing:

pattern.compile(RegExpInAForm_Field)

it will compile (and, by the way, assigns to pattern itself) no matter what 
is in the RegExp as you included it in a form field (yes, there can be 
online form fields where you include... regular expressions! I have one at
http://www.unitedscripters.com/spellbinder/greed.html  ). I mean that if 
you included slashes in the field, the compile method can read them right 
(without need of... escaping them).

BUT as soon as you either pass to a compile method or you assign to a 
RegExp upon initialization a reg exp string, there we go: neither the 
method nor the RegExp are any longer capable of taking care of the slashes 
escapeng them authomatically.

All this basically means this: in javaScript a slash followed by a d, which 
in regular expressions would mean \d a digit, in between quotes becomes an 
escaped d... therefore a string such
"hallo\d"
would be read as:
hallod

and NOT as hallo plus a digit (wehatever that may mean...)

Therefore you have to escape (escape means prepo9ning exactly a backward 
slash) all BACKWARD SLASHES you include:
"hallo\\d"
that is, TWO backward slashes.

Let's sum it up:

1) when initalizing a RegExp, and you pass a string either as argument or 
to  the built in compile method, you do not need the forward slashes
2) but whenever you include a backward slashes, you have to escape it with 
another backward slashes
3) step 2 doesn't apply in case you're sending data from a form field or 
repeatedly compiling in within a loop.

Enough for an headache I know, anyway I believe this would work:
new RegExp("course_\\d+_\\d+","ig");

May I know ask, by the way, what a string like "course_1_3" would mean?? :o)
I'm just kidding.

have a nice day, ciao

Alberto .·. Vallini
http://www.unitedscripters.com



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