Monthly Archives: December 2015

Hook All the Functions in JavaScript Files

During my daily development, I encounter a request to add code snippets before and after each function call for all the JavaScript files. I have figure out three ways to do this

1. Overwrite the, this will only effect the directly call the call method from a function object such as…). The call method will not triggered with directly call function with brace, such as foo(…)

disadvantage: not cover all the function even normal function calls

2. Use custom or use some AOP JS library to hook specify function. This is also could be extended by use a recursive method to hook all the function object in a give scope such as window in browser.

such as hooker lib,

jquery AOP plugin

advantage: easy to use

disadvantage: not cover all of the functions in the JS files, such as anonymous functions are not included.

3. Use some script to parse all the JS files and inject codes before and after all the functions.

This article is mainly to talk about the tool which I created for automatic inject the codes before and after the function calls.

It is called hookjs, which is written in python. It could be checkout from my github repo( The binary version could be download from the bin folder.

$ hookjs -h

usage: hookjs.exe [-h] [-p PATH] [-s START] [-e END]                   [-f [BLACK_FILES [BLACK_FILES ...]]]                   [-d [BLACK_DIRS [BLACK_DIRS ...]]]

A command line JavaScript hook tool for inject start, end codes into every JavaScript functions. Currently only support uncompressed EMCScipt 5. Any errors will be output into the error.log file.

optional arguments:

-h, –help   show this help message and exit

-p PATH, –path PATH  The path to the JavaScript file or directory

-s START, –start START  The start code snippet which will be injected at the                         begin of each function

-e END, –end END     The end code snippet which will be injected at the end                         of each function

-f [BLACK_FILES [BLACK_FILES ...]], –black-files [BLACK_FILES [BLACK_FILES ...]]                         Use regex expression to define the black files list, the files will not be hooked

-d [BLACK_DIRS [BLACK_DIRS ...]], –black-dirs [BLACK_DIRS [BLACK_DIRS ...]]                         Use regex expression to define the black dirs list, the directory and sub directory will not be searched

Created by Edwin, Shang(Shang, Erxin), License under GNU GPLv3. Version 1.0.0


Inject codes to a JS files, the original JS content

  1. x = findMax(1, 123, 500, 115, 44, 88);
  3. (function(){
  4. })();
  6. function findMax() {
  7. var i;
  8. var max = -Infinity;
  9. for (i = 0; i < arguments.length; i++) {
  10. if (arguments[i] > max) {
  11. max = arguments[i];
  12. }
  13. }
  14. return max;
  15. }


run command

  1. hookjs.exe -p e:\demo.js -s console.log("start"); -e console.log("end");
  1. x = findMax(1, 123, 500, 115, 44, 88);
  3. (function(){console.log(start);
  4. console.log(end);})();
  6. function findMax() {console.log(start);
  7. var i;
  8. var max = -Infinity;
  9. for (i = 0; i < arguments.length; i++) {
  10. if (arguments[i] > max) {
  11. max = arguments[i];
  12. }
  13. }
  14. console.log(end);return max;
  15. console.log(end);}



The tool is not works with compressed JS file such as jquery-min etc. To add hook for these kinds of JS files, it required to format the JS first then use the tool the inject the JS codes.

Current it is not design for support arrow function syntax which is added in EMCAScript 6

Have fun.

Automatic Export About:Config Content Compare the Difference between for Firefox


We need to compare the difference between the configuration changes between the new vision of the FF and the previous version

We wish to compare the configuration setting in plain text. Then we could use the compare tools such as beyond compare or winmerge to give us a quick visual for the difference.

The Problem:

There is not a official way to export the about:confg page from FF into plain text file. There is a prefs.js file locate in the firefox profile folder, it contains some of the configuration setting but not all.

Known solutions to export the about:config but not well enough:

Solution for export the about:config:

Use the GUI automation tool(autoit) to help export the configuration directly from the about:config page. The script is export-opened-firefox-config.au3 which could be download from my github repot

  1. Install autoit, which double be download from official website follow the previous link
  2. Download the export-opened-firefox-config.au3
  3. Before run the script close all the Firefox process existed in the current system
  4. Run the script export-opened-firefox-config.au3
  5. Open the Firefox that you want to export the about the configure content
  6. The script will start automatically and wait for it stops, please make any user input during the script execution
  7. The output.txt will be generated at the same location of the script file export-opened-firefox-config.au3 which contain all the configuration values
  8. Check the last line of the output.txt contain the last item of the about:config. If the values are same then all is well. If not please modify the sleep time for the script to give more calculate time for the low performance system.

Solution for generate the difference compilation results:

Use python to parse and generate the previous generate configuration files and the current user.js settings which contain in the LR-INSTALL-DIRECTORY\dat\FFProfile\user.js. The python script could be check out from my personal tools repo from github

  1. Install python 2.7.x, if current system doesn’t contain python environment
  2. Install xlsxwriter from pip or download the package install manually. Check this link, if you doesn’t familiar with python
  3. Download the script
  4. Copy and replace the about config content files and the user.js into the data folder to make it follow this file structure



5. Execute the python script the output files will be overwrite and generated automatically  Note: If the excel file is not required you could common the script lines relative to generate excel to only generate plain text report. The key/value pair is separate by semicolons like this:



Note: the content of the wiki may adapt to the old version of FF to check the new version please follow the link supplied in the wiki pages.