// SETUP
    var lotsOfVars = {};
    var oneVar = {};


    for (var i = 0; i < 10000; ++i) {
      lotsOfVars['var_' + i] = i;
    }



    oneVar['var_0'] = 20;




// TESTS
// many
var sum = 0;
for (var i = 0; i < 10000; ++i) {
  sum += lotsOfVars['var_' + i];
}

// one
var sum = 0;
for (var i = 0; i < 10000; ++i) {
  sum += oneVar['var_' + 0];
}