1.3.0 • Public • Published

Decofun – Debug tool

Decofun is a JavaScript function deanonymizer.

It parses your code and names any anonymous functions according to their context.

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Coverage Status

Version 1.2.x


npm i decofun


Command Line Tool

sudo npm -g i decofun

New from version 1.2.x we can simply use the deco executable in place of node to instrument anonymous functions.

deco examples/loadable

Since version 1.3.x the deco executable can also be instructed to use the cute-stack module to prettify stack traces, just add a --cute flag

deco examples/loadable --cute

To set the cute-stack's display type, pass it as the value of --cute

deco examples/loadable --cute table

To set the stack size pass a number

deco examples/loadable --cute 20

To set both the display type and number, pass a JSON array

deco examples/loadable --cute '["table", 20]'

Automatic Instrumentation

New from version 1.1.x, we can use decofun to automatically instrument any required modules, simply call the auto method, before requring any other modules

var myMod = require('./lib/myModule.js')
var somePub = require('somePublishedMod')

Both myMod and somePub will now have their anonymous functions named.

Alternatively, decofun can be called directly as a function (without supplying a path argument) to achieve the same result:

require('decofun')() # same as require('decofun').auto()
var myMod = require('./lib/myModule.js')
var somePub = require('somePublishedMod')

To undo automatic instrumentation and restore former behavior, simply use the restore method:

var decofun = require('decofun');;
var myMod = require('./aModToDebug')
var anotherMod = require('./noDebugNeededThx')

Client-side Instrumenting

For instrumenting browser code, you can use the deco-server module.

There is a live deco-server running on heroku, for instance we can deanonymize jQuery by with the following URL:

A deco transform is also planned for those who use browserify - for now we can simply use a deco-server to host our browserified code.

Programmatic Transform

We can transform any string containing JavaScript with the transform method.

var decofun = require('decofun')
var fs = require('fs');
var path = require('path')
var fixture = fs.readFileSync(path.join(__dirname, './fixture.js'));

As with the auto method, transforms can also be achieved with the polymorphic function representing the decofun module. When we pass a string to the decofun function, it executes a transform (and when we don't pass a string it calls

//same thing:


Run tests with

npm test


The examples folder is a good place to start.

To see how a direct transform would work, from the install directory we could run these commands:

cat node_modules/decofun/examples/transform/fixture.js #view the original 
node node_modules/decofun/examples/transform # view the result 

To see instrumentation upon require (the Auto feature), run the following:

cat node_modules/decofun/examples/auto/fixture.js #view the original 
node node_modules/decofun/examples/auto # view the result 

functions assigned to variables

Are labelled "of var | line N".

var myFn = function () {}

Transforms into:

var myFn = function asᅠvarᅠmyFnᅠㅣlineᅠ1 () {}

function parameters

Are labelled "passed into | line N".

someFunc('blah', function () {})

Transforms into:

someFunc('blah', function passedᅠintoᅠsomeFuncᅠㅣlineᅠ1 () {})

method parameters

Are labelled "passed into ː | line N".

obj.prop(function () { })

Transforms into:

obj.prop(function passedᅠintoᅠobjːpropᅠㅣlineᅠ1 () { })

sub-object method parameters

Are labelled "passed into ː | line N".

obj.subobj.prop(function () { })

Transforms into:

obj.subobj.prop(function passedᅠintoᅠsubobjːpropᅠㅣlineᅠ1 () { })

returned functions

Are labelled "returned from | line N".

function f() {return function () { }}

Transforms into:

function f() {return function returnedᅠfromᅠfᅠㅣlineᅠ1 () { }}

returned functions of returned anonymous functions

Are labelled "returned from ᐸ <parent function (named)> ᐳ | line N".

function contain () {
  return function () { 
    return function () {

Transforms into:

function contain() {
  return function returnedᅠfromᅠcontainᅠㅣlineᅠ2 () {
    return function returnedᅠfromᅠᐸᅠreturnedᅠfromᅠcontainᅠᐳᅠㅣlineᅠ3 () {

methods declared in object literals

Are labelled "as property ㅣ line N".

function contain () {
   return {
     propInLiteral: function () {}

Transforms into:

function contain() {
    return {
      propInLiteral: function asᅠpropertyᅠpropInLiteralᅠㅣlineᅠ3 () {}

methods assigned to instantiated objects

Are labelled "as property ㅣ line N".

var o = {}; o.p = function (cb) { }

Transforms into:

var o = {}; o.p = function asᅠpropertyᅠpᅠㅣlineᅠ1 (cb) { }

immediately invoked function expressions

Are labelled "IIFEㅣ line N".

!function() {}()

Transforms into:

!function IIFEᅠㅣlineᅠ1() {}()
;(function IIFEᅠㅣlineᅠ2(){}())


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