maettig/LICENSE.txt

## README.md

      
    Raw
  

              README.md
            
          
    Clean JavaScript code does not leak into the global variable scope. That's why we use strange looking stuff like (function() { var a = 'I am local'; })(); to execute code in a local scope. Inside such scopes, we can declare and use variables without conflict.
Since you often don't get a warning when using undeclared variables, I wrote an 140byt.es snippet to detect leaking variables. The idea is very simple and works in Opera and Firefox. Does not work in Internet Explorer.
Due to a bug in Firefox I had to add a try-catch block. Accessing or even checking the type of window.sessionStorage causes a "not supported" exception. It works fine without this in all other browsers. Another bug is that Firefox returns a getInterface method in the second call that was not there in the first call. I did not found out why this happens or how to prevent it. This is why I check for native functions. And (of course) there are problems in Internet Explorer. It does not store global variables in the window object so the function can't display anything. Replacing window with this does not help since it refers to the same object.
Click here to run the test script.

  
## annotated.js
function(a, b, c, d)                       //`window` (or something else) and three dummy arguments
{
  d = a[b = 'Leak:'                        //collect all info in string `b`
    ] = a[b] || { };                       //initialize the list of known properties, use `Leak:` as name
  for (c in a)                             //check everything in the `window` object
    try                                    //not required in Opera, but Firefox crashs for `sessionStorage`
    {
      d[c] ||                              //if this property is known from the previous call or
      /\[native code]/.exec(a[c])          //if this is a native function
        ? 1                                //then do nothing
        : b += '\n' + c + ' = ' + a[c],    //else add name and value to the string
      d[c] = 1                             //add this property to the list of known properties
    }
    catch (e) { }
  return b                                 //return the string
}

## index.js
function(a,b,c,d){d=a[b='Leak:']=a[b]||{};for(c in a)try{d[c]||/\[native code]/.exec(a[c])?1:b+='\n'+c+' = '+a[c],d[c]=1}catch(e){}return b}

## LICENSE.txt
            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2012 Thiemo Mättig <http://maettig.com>

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.

## package.json
{
  "name": "dumpGlobalLeaks",

  "description": "Debugging helper dumps all variables that leaked into the global scope.",

  "keywords": [
    "debugging",
    "global",
    "scope",
    "test",
    "variables",
  ]
}

## test.html
<!DOCTYPE html>
<script type="text/javascript">
// 140 bytes
var dumpGlobalLeaks = function(a, b, c, d) //`window` (or something else) and three dummy arguments
{
  d = a[b = 'Leak:'                        //collect all info in string `b`
    ] = a[b] || { };                       //initialize the list of known properties, use `Leak:` as name
  for (c in a)                             //check everything in the `window` object
    try                                    //not required in Opera, but Firefox crashs for `sessionStorage`
    {
      d[c] ||                              //if this property is known from the previous call or
      /\[native code]/.exec(a[c])          //if this is a native function
        ? 1                                //then do nothing
        : b += '\n' + c + ' = ' + a[c],    //else add name and value to the string
      d[c] = 1                             //add this property to the list of known properties
    }
    catch (e) { }
  return b                                 //return the string
}
var goodFunction = function(a)             //`a` is an unused argument, it's declared but not initialized
{
  a = 1;                                   //initialize `a`
  var b;                                   //declare `b`
  b = 2;                                   //initialize `b`
  var c = 3;                               //declare and initialize `c` in a single statement
}
var badFunction = function()
{
  a = 1;                                   //leaks to the global scope since it's undeclared in the function
}
dumpGlobalLeaks(window);                   //first call returns everything, this should be ignored
goodFunction();                            //call the non-leaking function
alert(dumpGlobalLeaks(window));            //should display an empty leak dump
badFunction();                             //call the leaking function
alert(dumpGlobalLeaks(window));            //should display a leak dump with `number a = 1`
</script>
	function(a, b, c, d) //`window` (or something else) and three dummy arguments
	{
	d = a[b = 'Leak:' //collect all info in string `b`
	] = a[b] \|\| { }; //initialize the list of known properties, use `Leak:` as name
	for (c in a) //check everything in the `window` object
	try //not required in Opera, but Firefox crashs for `sessionStorage`
	{
	d[c] \|\| //if this property is known from the previous call or
	/\[native code]/.exec(a[c]) //if this is a native function
	? 1 //then do nothing
	: b += '\n' + c + ' = ' + a[c], //else add name and value to the string
	d[c] = 1 //add this property to the list of known properties
	}
	catch (e) { }
	return b //return the string
	}
	DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
	Version 2, December 2004

	Copyright (C) 2012 Thiemo Mättig <http://maettig.com>

	Everyone is permitted to copy and distribute verbatim or modified
	copies of this license document, and changing it is allowed as long
	as the name is changed.

	DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
	TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

	0. You just DO WHAT THE FUCK YOU WANT TO.
	{
	"name": "dumpGlobalLeaks",

	"description": "Debugging helper dumps all variables that leaked into the global scope.",

	"keywords": [
	"debugging",
	"global",
	"scope",
	"test",
	"variables",
	]
	}
	<!DOCTYPE html>
	<script type="text/javascript">
	// 140 bytes
	var dumpGlobalLeaks = function(a, b, c, d) //`window` (or something else) and three dummy arguments
	{
	d = a[b = 'Leak:' //collect all info in string `b`
	] = a[b] \|\| { }; //initialize the list of known properties, use `Leak:` as name
	for (c in a) //check everything in the `window` object
	try //not required in Opera, but Firefox crashs for `sessionStorage`
	{
	d[c] \|\| //if this property is known from the previous call or
	/\[native code]/.exec(a[c]) //if this is a native function
	? 1 //then do nothing
	: b += '\n' + c + ' = ' + a[c], //else add name and value to the string
	d[c] = 1 //add this property to the list of known properties
	}
	catch (e) { }
	return b //return the string
	}
	var goodFunction = function(a) //`a` is an unused argument, it's declared but not initialized
	{
	a = 1; //initialize `a`
	var b; //declare `b`
	b = 2; //initialize `b`
	var c = 3; //declare and initialize `c` in a single statement
	}
	var badFunction = function()
	{
	a = 1; //leaks to the global scope since it's undeclared in the function
	}
	dumpGlobalLeaks(window); //first call returns everything, this should be ignored
	goodFunction(); //call the non-leaking function
	alert(dumpGlobalLeaks(window)); //should display an empty leak dump
	badFunction(); //call the leaking function
	alert(dumpGlobalLeaks(window)); //should display a leak dump with `number a = 1`
	</script>