Optimization for RegExp

[garycourt]

At the time of this issue, Prepack is compiling new RegExps from this:

global.a = /abc/;

to this:

(function () {
  var _$0 = RegExp;
  var _$1 = Object.defineProperty;

  var _0 = _$0("abc", "");

  var $$0 = {
    enumerable: false,
    configurable: false,
    writable: true
  };
  $$0.value = 0;

  _$1(_0, "lastIndex", $$0);

  a = _0;
})();

I am highly skeptical that this is faster at runtime then the original code. Please correct me if I'm wrong.

[NTillmann]

I have noticed that as well. It can certainly better. When I looked at it myself, I got a bit confused as to whether all browsers define the same special properties on RegEx, that's something else to look into. In any case, a freshly defined RegExp shouldn't need any such property definitions.

[jacktuck]

What about ReDOS? Could that path be optimized?

https://www.owasp.org/index.php/Regular_expression_Denial_of_Service_-_ReDoS

[hermanventer]

I'm not sure what you are asking. Are you concerned about evil regexp strings breaking Prepack, or are you asking if Prepack could find vulnerable uses of regexp in the code it is prepacking?