symbol lookup performance

In javascript symbols can be used as keys to store private values like so:

sig = Symbol "self"

ob = {}

ob.self = null

ob[sig] = null

symbol_look = function()
{
  ob[sig] = Math.random()
}
normal_look = function()
{
  ob.self = Math.random()
}

The private value self is accessible publicly while the one using sig is not, I was curious to know if there was significant performance penalty for using symbols.

symbol_look x 56,957,738 ops/sec ±1.49% (85 runs sampled)
normal_look x 57,632,100 ops/sec ±1.81% (87 runs sampled)

In my tests using benchmark.js it seemed there was none, so if you are in a stuck in a situation where you have to choose but are concerned about the performance penalty, you can rest assured it will not be a problem.