Javascript Regular Expression help

[§§}Associus]

The more I learn about regular expressions, the more I realize how much I really don't know about them...

I'm trying to create a regular expression to do the following.

Have a "list" setup in a regular expression as a pattern something like /(1|2|5|8|11|21)/ and use it to parse search for a match in a variable, let's call it mem_group.

I had thought to use an array of different regular expressions containing varying quantities of numberse to search for. Something like...

var allowed_groups = new Array;
allowed_groups[0] = "/(1|2|5|8|11|21)/ ";
allowed_groups[1] = "/(2|4|5|9|15)/";
allowed_groups [2] = "/6|8|27/";
etc.

If the number of items to search for were identical in each case, I could simply have used an array of identically sized arrays and then searched through it with do while or for loop. However, since the lists of values to search for vary in length, I do not know how to do that as I'm not aware of any Javascript support for arrays of varying length.

The mem_group variable will store a single number value. Hopefully the variable will be a string type, but as I'm assigning the value to mem_group from an option "value" out of a select/option construct, I'm not sure if it is of string or integer type.

What I want the regular expression to do is let me know if the value stored in mem_group exactly equals any one of the "values" listed in the regexp pattern that are separated by the "|" alternation characters.

Examples of desired results:

using some form of a regular expression like /(1|3|5|8|11|21)/
mem_group = 1
result of match = 1

mem_group = 3
result of match = 3

mem_group = 10
result of match = no match
(the "1" in the regexp must not "match" on the "1" that begins the value of 10 in mem_group.)

mem_group = 11
result of match = 11

mem_group = 15
result of match = no match
(again the "5" in the regexp must not match the ending "5" that ends the value of 15 in mem_group.)

In other programming languages, I might use set intersections to look for a match, but I do not know of any set operations in Javascript.

If there is a better way to do this than regular expressions, I'm open to that as well as I'm not set on a particular type of solution to my problem.

Any advice or insight would be greatly appreciated.

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Edit:

I did some testing and figured out that JS does support non-identically sized arrays within an array. However, if someone does know of a way to look for a match using a regular expression in this scenario, I'd love to learn how to do it.

Thanks,

[Jordan]

If I'm reading your post correctly, all you need to do is add ^ and $ to indicate the beginning and end of the string. The way you have it now would allow 21 in the mem_group variable to match the 1 or 21 in /(1|3|5|8|11|21)/.

So it should look like this.

/^(1|3|5|8|11|21)$/

[§§}Associus]

Thanks Jordan,

That appears to be working like what I was looking for.

I knew my example regular expression did not have just what it needed, but I think I was thinking that I needed to look for something more obscure that the solution. I did not include it in my example, but I was thinking that I somehow needed to include the word boundaries as part of the expression but the only thing I had come up with previously was /\b(1|3|9|10)\b/ but that did not achieve the desired result.

I've seen the "^" and "$" used at the beginning and end (respectively) of regular expressions before but never really understood what they did. Now I believe the light has dawned.

Using this regular expression method will be much simpler than me looping through an array and it will probably execute faster as well.

Thanks again.

[Jordan]

Glad to help. You had the right idea with the boundaries, and if you ever find yourself in the same situation search Google for "javascript regexp cheat sheet" and some great webpages will come up that have almost everything that you can use in Javascript's regular expressions.

[§§}Associus]

Thanks for the tip.

I have used Google to search for information on regular expressions but never thought to look for cheat sheets. I've found some great stuff already.

[Jordan]

No problem. Once you get the syntax figured out it's pretty easy unless you are having to search for a very dynamic and complicated string.