Problem with Actionscript Regular Expressions

Question

I have to parse out color information from HTML data. The colors can either be RGB colors or file names to a swatch image.

I used http://www.gskinner.com/RegExr/ to develop and test the patterns. I copied the AS regular expression code verbatim from the tool into Flex Builder. But, when I exec the pattern against the string I get a null.

Here are the patterns and an example of the string (I took the correct HTML tags out so the strings would show correctly):

DIV data:

<div style="background-color:rgb(2,2,2);width:10px;height:10px;">

DIV pattern:

/([0-9]{1,3},[0-9]{1,3},[0-9]{1,3})/

IMG data:

<img src="/media/swatches/jerzeesbirch.gif" width="10" height="10" alt="Birch">

IMG pattern:

/[a-z0-9_-]+/[a-z0-9_-]+/[a-z0-9_-]+\.[a-z0-9_-]+/

Here's my Actionscript code:

var divPattern : RegExp = new RegExp("/([0-9]{1,3},[0-9]{1,3},[0-9]{1,3})/");
var imgPattern : RegExp = new RegExp("/[a-z0-9_-]+/[a-z0-9_-]+/[a-z0-9_-]+\.[a-z0-9_-]+/");

var divResult : Array = divPattern.exec(object.swatch);
var imgResult : Array = imgPattern.exec(object.swatch);  

Both of the arrays are null.

This is my first foray into AS coding, so I think I'm declaring something wrong.

Steve

Answer 1

(I don't know ActionScript but I know Javascript and they should be close enough to solve your problem.)

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To construct a RegExp object for e.g. the pattern ^[a-z]+$, you either use

var pattern : RegExp = new RegExp("^[a-z]+$");

or, better,

var pattern : RegExp = /^[a-z]+$/

The code new RegExp("/^[a-z]+$/") is wrong because this expects a slash before the ^ and after the $.

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Therefore, your DIV pattern should be written as

var divPattern : RegExp = /([0-9]{1,3},[0-9]{1,3},[0-9]{1,3})/;

but, as you know, the ( and ) are special characters for capturing, you need to escape them:

var divPattern : RegExp = /\([0-9]{1,3},[0-9]{1,3},[0-9]{1,3}\)/;

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For the IMG pattern, as / delimitates a RegEx, you need to escape it as well:

var imgPattern : RegExp = /[a-z0-9_-]+\/[a-z0-9_-]+\/[a-z0-9_-]+\.[a-z0-9_-]+/

---

Finally, you could use \d in place of [0-9] and \w in place of [a-zA-Z0-9_].

Answer 2

I don't know enough to tell if your regex patterns are correct, but from the docs on the AS3 RegExp class, it looks like your new RegExp() call needs a second argument to declare flags for case sensitivity etc.

EDIT: Also, as Bart K has pointed out, you don't need the / delimiters when using the new method.

So you can use either:

var divPattern:RegExp = new RegExp("([0-9]{1,3},[0-9]{1,3},[0-9]{1,3})", "");

OR you can also use the alternate syntax with /:

var divPattern:RegExp = /([0-9]{1,3},[0-9]{1,3},[0-9]{1,3})/;

... in which case the flag string (if any) is included after the final /