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0.1.0 • Public • Published


A lightweight profiling tool for javascript.

Wraps standalone functions or member functions in objects and classes, traces execution time and reports results.

Doesn't utilize V8 profiler or anything terribly node-specific at its core so browser version should appear someday soon.


  • Profile standalone functions, all functions in object, or all functions in a class prototype.
  • Customize profiler granurality - differentiate method calls by arguments or group several methods together.
  • Don't worry about synchronous callbacks - they are treated as return by default.
  • Choose from one of three report types to get perspective you need:
    • Plain report, sortable by number of calls, total execution time, or own execution time (excl. nested executions)
    • Tree report to get perspective of the call stack
    • Hotspots report to identify and track most time consuming calls


This is kind of release candidate. I'm trying to finalize basic features and API for initial stable version (1.0.0). I do not plan any dramatic API changes at this point, unless I realize some serious design flaw.

Example use and output

Use lightprof like this:

// import and initialize Profiler
var Profiler = require('lightprof').Profiler,
    profiler = new Profiler();
//something to profile
var Class = function Class() { ... }
Class.prototype.method = function() { ... }
var instance = new SomethingElse();
// start profiling 'instance' object and any instances of 'Class' created after this point
profiler.profile(instance, Class);
//... do your stuff, e.g. 'instance.foobar()' and 'new Class().method()' ...
// stop profiling, replace traced functions with originals
// output a tree report

To get results like this:

function                                       calls     total time [ms]
├Class.method3                                    2         2015.961540
│├Class.method                                    4         1512.021972
││└Class.method2                                  4         1439.995954
│└Class.method2                                   2          479.940796
├Class.method                                     1          315.033041
│└Class.method2                                   1          299.979859
├Class.method2                                    1          179.981357
├SomethingElse.foobar                             1           97.053809
│├                               1           48.971801
│└                               1           23.983303
├                                2           44.518808
└                                1           20.926568

Important notes

  • 'class' names in reports are in fact names of constructor functions. You need to have named constructor function to see it in report: var Class = function Class() { ... } (and not anonymous: var Class = function() { ... })
  • the same applies for standalone functions: do not profile anonymous functions (var fn = function() { ... })


Profiler constructor options


Boolean, default: false

When set to true, arguments passed to profile() may be strings which will be evaled to - names of objects or classes to profile.


Boolean, default false.

When true, profile() will start paused (not recording function calls, just tracing call stack). Call resume() to start recording in such case.


Boolean, default true

Tells the profiler whether calling a callback function should be considered as end of function execution. Callback is assumed to be the last argument passed to the profiled method (if it is a function).


Function(constructorName, functionName, args)


function (constructorName, functionName, args) {
  return (constructorName? constructorName + '.' : '') + functionName;

Assigns a name to method call. Default implementation produces names in form of 'ClassName.methodName', which results in expected profiler behavior.

However, by overriding this function, you can

  • add more granurality by generating different names for method calls with different arguments or
  • reduce granurality by grouping different method calls in one name, or
  • i don't know, whatever ;)
var profiler = new Profiler({
    nameFn: function (constructorName, functionName, args) {
        var argTypes = _.chain(args).flatten()
            .map(function(arg){ return typeof(arg) })
   return (constructorName? constructorName + '.' : '') + functionName + '(' + argTypes + ')';
function doSomething() {
doSomething = profiler.profile(doSomething);
doSomething(1, 2);
// ==>
//  function                                calls       own time [ms]     total time [ms]
//  doSomething()                              1               12.48               12.48
//  doSomething(number, number)                1               15.01               15.01

.profile( what... )

Accepts any number of arguments, each of which can be:

  • Class (= constructor function). Wraps all functions in its prototype object.
  • Object. Wraps all its functions.
  • Function (with empty prototype object). Returns wrapped function (does not continue wrapping following arguments if any). Note that you need to call wrapped function (not the original) to allow profiling - see the example above.


Temporarily stops recording calls and execution times. All data and wrappers are left intact, ready to resume recording.


Resume recording after paused.


Stops profiling and replaces wrappers back with original functions. Collected data are kept for report methods.

.reportPlain( options )

default options:

    orderBy: 'timeOwn', // one of ['timeOwn', 'timeTotal', 'calls']
    timeUnit: 'ms' // one of [s, ms, us, ns]

example output:

function                   calls       own time [ms]     total time [ms]
Class.method2                 8             2399.88             2399.88
Class.method                  5               87.05             1827.04             2               69.89               69.89

.reportTree( options )

default options:

    timeUnit: 'ms' // one of [s, ms, us, ns]

example output:

function                                       calls     total time [ms]
├Class.method3                                    2         2015.961540
│├Class.method                                    4         1512.021972
││└Class.method2                                  4         1439.995954
│└Class.method2                                   2          479.940796
└                                1           20.926568

.reportHotspots( options )

default options:

    timeUnit: 'ms', // one of [s, ms, us, ns]
    records: 10 // number of hotspots reported.

example output:

function                                       calls       own time [ms]
 └Class.method2                                   4             1440.01
└Class.method2                                    2              479.93
└Class.method2                                    1              299.99
Class.method2                                     1              179.95


Reinitializes profiler, clearing all data. Call this only to reuse existing Profiler instance - in between .stop(); .reportXXX() and another .profile()

What's next

  • Proper tests
  • Better documentation
  • Browser version




npm i lightprof

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  • tomkmec