V8 Engine cached target string of pattern match.

v8_regexp_cache.js

var assert = function(expr, msg){
  var message = 'Assertion failed';
  if(msg) message += ': ' + msg;
  if(!expr) throw new Error(message);
};

var matchResultA;

(function(){
  var A =  RegExp('.');
  matchResultA = A.exec('foo')[0];
})();

(function(){
  var B = new RegExp('.');
  var C = new RegExp('.');

  assert( B !== C, 'B and C are diffent object' );

  var matchResultB = B.exec()[0];
  var matchResultC = C.exec()[0];

  assert( matchResultA === matchResultB, 'Pattern match result of B equals result of A' );
  assert( matchResultB === matchResultC, 'Pattern match result of C equals result of B' );

  assert( matchResultA === /./.exec()[0] );
  assert( /.../.exec()[0] == 'foo' );

  // String 'foo' cached by V8?
})();