JS: Simple JavaScript profiler

gistfile1.js

/**
 * Simple profiler, used to measure time taken by processes.
 * Usage:
 * <pre>
 * var profile = new mpProfiler("Measuring async loop");
 *     i;
 * for (i = 0; i < 10; i++) {
 *     // do something really cpu expensive
 *     doExpensiveJob(i, 10, function(pos, total){
 *         profile.addStep("Step " + cur + " from " + total + " done!");
 *         if (pos === total) {
 *             // the end is reached
 *             var results = profile.end();
 *             // dump the results containg detailed measurement infoes
 *             console.log(results);
 *         }
 *     });
 * }
 * </pre>
 *
 * @class mpProfiler
 * @constructor
 * @param  {String}  [msg=""]
 */
var mpProfiler = function(msg) {
   this.start(msg);
};

/**
 * Starts a timer.
 * @method start
 * @param  {String}  [msg=""]  Description of started timer
 */
mpProfiler.prototype.start = function(msg) {
   this._msg = msg || "";
   this._start = new Date().getTime();
   this._end = null;
   this._diffTotal = null;
   this._steps = [];
};

/**
 * Add a step to a specific timer.
 * @method addStep
 * @param  {String}  [msg=""]  Description of the step
 * @return  {Object}  Containing details about the timer step.
 */
mpProfiler.prototype.addStep = function(msg) {
   msg = msg || "";

   var start = new Date().getTime(),
       lenSteps = this._steps.length,
       diff = 0, diffTotal = start - this._start,
       curStep;

   if (lenSteps > 0) {
       diff = start - this._steps[lenSteps-1].start;
   }

   curStep = {
       start: start,
       msg: msg,
       diff: diff,
       diffTotal: diffTotal
   };

   this._steps.push(curStep);

   return curStep;
};

/**
 * Ends a running timer and returns all collected results.
 * @method end
 * @param  {Boolean}  [flush=false]  Flag to flush results to logger (console.log, if available)
 * @return  {Object}  Containing details about the timer including all steps.
 */
mpProfiler.prototype.end = function(flush) {
   flush = flush || false;

   var end = new Date().getTime(),
       result = {};

   this._end = end;
   this._diffTotal = end - this._start;

   result = {
       msg: this._msg,
       start: this._start,
       end: this._end,
       diffTotal: this._diffTotal,
       steps: this._steps
   };

   if (flush) {
       if ("undefined" !== typeof console) {
           console.log("mpProfiler result", result);
       }
   }

   return result;
};