I would like to dynamically construct a regex pattern in AS3

Question

I would like to dynamically create the Regular Expression in the code below, by working out the permutations I need to detect for, then creating the Regular Expression like concatenating a string, but no matter what I try it fails.

I've found that if you trace testRX.source, you can see the regexp without escape characters ( thats what I believe anyway ).

Ideally I would like to do this

var permutationsString:String = "abc|acb|bac|bca|cab|cba";
var regex1:RegExp = "/\b("+permutationsString+")\b/g";
regex1.test( "whatever" );

but it does not work.

Here's working code below

var testRX:RegExp = /\b(abc|acb|bac|bca|cab|cba)\b/g;

var regex:RegExp = new RegExp( testRX );

trace( "regex.test = " + regex.test( "333" )); // false

trace( "regex.test = " + regex.test( "abc" )); // true

trace( "regex.test = " + regex.test( "ca"  )); // false

trace( "regex.test = " + regex.test( "bbb" )); // false

trace( "regex.test = " + regex.test( "abce")); // false

This is Actionscript 3.

Thanks in advance.

gingerman

BadFeelingAboutThis · Accepted Answer · 2015-07-09 20:30:35Z

2

You need to remove the first forward slash (as that is just for starting a RexEx literal which you aren't doing now that you're building a string), escape the backslashes (since you're creating a string literal), and move the regex flags into the second parameter of the RexEx constructor:

var regex1:RegExp = new RegExp("\\b(" + permutationsString + ")\\b","/g");

This should then do what you'd like.

answered Jul 9, 2015 at 20:30

BadFeelingAboutThis

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gingrrr Over a year ago

Batman your reputation is well deserved. Thanks that works perfectly.

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