time_conditionals.js

Compare = function(fn1, fn2, i) {
  var time = function(fn) {
    var now = new Date();
    fn();
    return new Date() - now;
  },
  spinOn = function(fn, i) {
    return function() { for (var ii = i;ii;ii--) fn(); }
  },
  fn1_time = time(spinOn(fn1, i)),
  fn2_time = time(spinOn(fn2, i));
  
  console.log('function 1 took: %o', fn1_time);
  console.log('function 2 took: %o', fn2_time);
};

Compare(
  function() { var a = true, b = 1; if (a) b; },
  function() { var a = true, b = 1; !a && b; },
  10000000
);
Compare(
  function() { var a = false, b = 1; if (a) b; },
  function() { var a = false, b = 1; !a && b; },
  10000000
);

Compare(
  function() { var a = true, b = 1, c = 2; if (a) b; else c; },
  function() { var a = true, b = 1, c = 2; !a && b; a && c; },
  10000000
);
Compare(
  function() { var a = false, b = 1, c = 2; if (a) b; else c; },
  function() { var a = false, b = 1, c = 2; !a && b; a && c; },
  10000000
);