core-js/modules/es6.regexp.constructor.js

Standard library

var $       = require('./$')
  , global  = require('./$.global')
  , cof     = require('./$.cof')
  , $flags  = require('./$.flags')
  , $RegExp = global.RegExp
  , Base    = $RegExp
  , proto   = $RegExp.prototype
  , re      = /a/g
  // "new" creates a new object
  , CORRECT_NEW = new $RegExp(re) !== re
  // RegExp allows a regex with flags as the pattern
  , ALLOWS_RE_WITH_FLAGS = function(){
    try {
      return $RegExp(re, 'i') == '/a/i';
    } catch(e){ /* empty */ }
  }();

if(require('./$.support-desc')){
  if(!CORRECT_NEW || !ALLOWS_RE_WITH_FLAGS){
    $RegExp = function RegExp(pattern, flags){
      var patternIsRegExp  = cof(pattern) == 'RegExp'
        , flagsIsUndefined = flags === undefined;
      if(!(this instanceof $RegExp) && patternIsRegExp && flagsIsUndefined)return pattern;
      return CORRECT_NEW
        ? new Base(patternIsRegExp && !flagsIsUndefined ? pattern.source : pattern, flags)
        : new Base(patternIsRegExp ? pattern.source : pattern
          , patternIsRegExp && flagsIsUndefined ? $flags.call(pattern) : flags);
    };
    $.each.call($.getNames(Base), function(key){
      key in $RegExp || $.setDesc($RegExp, key, {
        configurable: true,
        get: function(){ return Base[key]; },
        set: function(it){ Base[key] = it; }
      });
    });
    proto.constructor = $RegExp;
    $RegExp.prototype = proto;
    require('./$.redef')(global, 'RegExp', $RegExp);
  }
}

require('./$.species')($RegExp);