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Written by Oleksandr Gavenko (AKA gavenkoa), compiled on 2017-01-30 from rev ccaa2f364422+.

Develop with/of Firefox.

Useful Firefox add-ons for developers.

https://addons.mozilla.org/en-US/firefox/collections/mozilla/webdeveloper/
Plug-ins for Web-development.

Firebug.

Firebug integrates with Firefox to put a wealth of development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.

http://getfirebug.com
home page
https://addons.mozilla.org/firefox/addon/1843
download page

Live HTTP Headers.

  • First by adding a 'Headers' tab in 'View Page Info' of a web page.
  • Second by adding a tool in the 'Tools->Web Development' menu to be able to display http headers in real time (while pages are being downloaded from the Internet.
  • Third by letting you edit request headers and replay an URL (beta). Look for the Replay button in the live window!

This project may be of some help for the following:

  • Help debugging web application.
  • See which kind of web server the remote site is using.
  • See the cookies sent by remote site.

Alternatively you can use fiddler2 (only Windows as it written in .NET)

http://livehttpheaders.mozdev.org/
home page
https://addons.mozilla.org/en-US/firefox/addon/3829/
download page
http://www.fiddler2.com/fiddler2/
Web Debugging Proxy

Wappalyzer.

Reverse which libraries and frameworks used by page.

https://addons.mozilla.org/en-US/firefox/addon/wappalyzer/
download page

Tamper Data.

  • Use tamperdata to view and modify HTTP/HTTPS headers and post parameters.
  • Trace and time http response/requests.
  • Security test web applications by modifying POST parameters.

Based on code and incompotable with "Live HTTP Headers" extensions.

http://tamperdata.mozdev.org/index.html
home page
https://addons.mozilla.org/en-US/firefox/addon/966/
download page
http://jimbojw.com/wiki/index.php?title=Tamper_Data
Tamper Data tutorial.

Extension security.

Debugging in Firefox.

For JavaScript:

// Enables strict JavaScript warnings in the Error Console.
user_pref("javascript.options.strict", true);
// Logs errors in chrome files to the Error Console. Enable Components.utils.reportError().
user_pref("javascript.options.showInConsole", true);
// Disables the XUL cache so that changes to windows and dialogs do not require a restart.
user_pref("nglayout.debug.disable_xul_cache", true);
// Enables the use of the dump() statement to print to the standard console.
user_pref("browser.dom.window.dump.enabled", true);
// This enables to run JavaScript code snippets in the chrome context of the Scratchpad from the Tools menu.
user_pref("devtools.chrome.enabled", true);
// This will send more detailed information about installation and update problems to the Error Console.
user_pref("extensions.logging.enabled", true);
user_pref("dom.report_all_js_exceptions", true);
// This adds a "Browser Debugger" entry to the "Web Developer" submenu of the "Tools" menu.
// The Browser Debugger can be used to debug the JavaScript code of extensions.
user_pref("devtools.debugger.remote-enabled", true);
// Detect deprecated code use.
user_pref("devtools.errorconsole.deprecation_warnings", true);

Examine devtool options in about:config with prefix devtools.:

user_pref("devtools.debugger.enabled", true);
user_pref("devtools.debugger.pause-on-exceptions", true);
user_pref("devtools.debugger.auto-pretty-print", true);

user_pref("devtools.debugger.chrome-debugging-host", "localhost");
user_pref("devtools.debugger.chrome-debugging-port", 6080);
user_pref("devtools.debugger.ignore-caught-exceptions", true);
user_pref("devtools.debugger.remote-enabled, true);
user_pref("devtools.debugger.remote-host", "localhost");
user_pref("devtools.debugger.remote-port", 6000);
https://developer.mozilla.org/en/Setting_up_extension_development_environment
Setting up profile, options and about developer plugin.
https://developer.mozilla.org/en-US/docs/Tools/Debugger
JavaScript Debugger.
https://getfirebug.com/doc/breakpoints/demo.html
Conditional Network Breakpoints. Breakpoints on DOM (HTML) Mutation Events. Breakpoints on DOM Property Changes. Breakpoints on Errors.

Debugging JavaScript with Web Console.

Instead of "Error Console" (press Ctrl+Shift+J) use "Web Console" (press Ctrl+Shift+K) in Firefox >=4.0:

console.log("str");
console.info("str is %s", "str");
console.warn("this is %o", this);
console.error("int: %i, float: %f, string: %s, object: %o", 2, .333, "str", this);

To see stack-trace use:

console.trace();
console.log(new Error().stack);

See:

Debugging JavaScript with Firebug.

With Firebug you can use 'console.log(obj)' for logging. Also output can be grouped with console.group("name") to start a new indentation block, and then console.groupEnd().

Same but with different coloring do 'console.debug', 'console.info', 'console.warn', and 'console.error' functions.

http://getfirebug.com/logging
logging
http://getfirebug.com/wiki/index.php/Console_API
Console API
http://getfirebug.com/wiki/index.php/Command_Line
Command Line
http://getfirebug.com/wiki/index.php/Console_Panel
Console Panel

dump().

Set in about:config browser.dom.window.dump.enabled to true.

All messages go to native console. On Windows this require -console option for firefox.exe.

https://developer.mozilla.org/en/DOM/window.dump

Components.utils.reportError.

Write error msg to Error console (not in Web Console):

Components.utils.reportError("msg");
// Show the error console.
toJavaScriptConsole();

Firefox 3.x require set preference 'javascript.options.showInConsole' to 'true' which is default value fro Firefox 4.x.

Build Firefox from sources.

https://developer.mozilla.org/en/Build_Documentation
Build Instructions
https://developer.mozilla.org/en/Mozilla_Source_Code_%28Mercurial%29
Getting Mozilla Source Code Using Mercurial

Native Firefox debugging.

Adding symbols from Symbol Server.

Execute in WinDbg:

.sympath SRV*c:\symcache\*http://msdl.microsoft.com/download/symbols;SRV*c:\symcache\*http://symbols.mozilla.org/firefox

or Ctrl+S and add:

SRV*c:\symcache\*http://msdl.microsoft.com/download/symbols;SRV*c:\symcache\*http://symbols.mozilla.org/firefox

See:

https://developer.mozilla.org/en/Using_the_Mozilla_symbol_server