GitHub - my8bird/nodejs-timeit: Provides for running a function multiple times and recording how long it took. Useful for determining if one approach is faster then another.

npm install timeit
or
git clone git@github.com:my8bird/nodejs-timeit.git
npm install

var timeit = require('./timeit'),
    iterations = 30000;

function use_concat(done) {
    var a = 'a string',
        b = a.concat('stuck together');
    done();
}

timeit.howlong(iterations, use_concat, function(err, results) {
   console.log('Baseline',      results[0]);
   console.log('Concat speed', results[1]);
});

var timeit = require('./timeit'),
    iterations = 30000;

function use_concat(done) {
    var a = 'a string',
        b = a.concat('stuck together');
    done();
}

function use_plus(done) {
   var a = 'a string',
       b = a + 'stuck together';
   done();
}

timeit.howlong(iterations, [use_concat, use_plus], function(err, results) {
   console.log('Baseline',         results[0]);
   console.log('Concat speed',     results[1]);
   console.log('Using Plus speed', results[2]);
});

Baseline { total_runtime: 151,
  total_step_runtime: 28,
  average_step_runtime: 0.0009333333333333333 }
Concat speed { total_runtime: 149,
  total_step_runtime: 36,
  average_step_runtime: 0.0012,
  total_off_baseline: -2,
  total_step_off_baseline: 8,
  average_step_off_baseline: 0.00026666666666666657 }
Using Plus speed { total_runtime: 141,
  total_step_runtime: 44,
  average_step_runtime: 0.0014666666666666667,
  total_off_baseline: -10,
  total_step_off_baseline: 16,
  average_step_off_baseline: 0.0005333333333333334 }