So my string is something like "BlaBlaBlaDDDaaa2aaa345" I want to get rid of its sub string which is "BlaBlaBlaDDD" so the result of operation will be a string "aaa2aaa345" How to perform such thing with actionscript?
I'd just use the String#replace method with a regular expression:
var string:String = "BlaBlaBlaDDD12345";
var newString:String = string.replace(/[a-zA-Z]+/, ""); // "12345"
That would remove all word characters. If you're looking for more complex regular expressions, I'd mess around with the online Rubular regular expression tester.
This would remove all non-digit characters:
var newString:String = string.replace(/[^\d]+/, ""); // "12345"
If you know the exact string you want to remove, then just do this:
var newString:String = string.replace("BlaBlaBlaDDD", "");
If you have a list (array) of substrings you want to remove, just loop through them and call the string.replace
method for each.