CODING_STANDARDS

  1. File Formatting
  ==================

  1.1. General
  ============

  For files that contain Javascript code, it's header must consist of a license
block, referring to the GNU LGPL (Lesser General Public License) and a reference
to the NOTICE file, which contains copyright information and license types of
third party code and derivative works.
  It's RECOMMENDED that a Javascript file starts with a compiler directive,
telling the compiler[1] that it should be included in debug and release builds:

#
#  // #ifdef __WITH_APP
#

  If a Javascript file contains the statement above, it SHOULD also end with a
closing statement:

#
#  // #endif
#

  1.2. Indentation
  ================

  Indentation should consist of 4 spaces. Tabs are not allowed.

  1.3. Maximum Line Length
  ========================

  The target line length is 80 characters. That is to say, apf developers should
strive keep each line of their code under 80 characters where possible and
practical. However, longer lines are acceptable in some circumstances.
The maximum length of any line of code is 120 characters.

  1.4. Line Termination
  =====================

  Line termination follows the Unix text file convention. Lines must end with a
single linefeed (LF) character. Linefeed characters are represented as
ordinal 10, or hexadecimal 0x0A.

  Note: Do not use carriage returns (CR) as is the convention in Apple OS's
(0x0D) or the carriage return/linefeed combination (CRLF) as is standard for the
Windows OS (0x0D, 0x0A).

  2. Naming Conventions
  =====================

  2.1 Classes

  The root level directory of the apf standard library is the "core/" directory.
The root level directory of the apf elements is the "elements/" directory.
The root level directory of the apf Teleport library and its modules is the
"elements/teleport/" directory.

  Class names may only contain alphanumeric characters. Numbers are permitted
in class names but are discouraged in most cases.

  If a class name is comprised of more than one word, the first letter of each
new word must be capitalized. Successive capitalized letters are not allowed,
e.g. a class "parserJML" is not allowed while "parserJml" is acceptable.

  2.2. Filenames
  ==============

  For all other files, only alphanumeric characters, underscores, and the dash
character ("-") are permitted. Spaces are strictly prohibited.

  Any file that contains Javascript code should end with the extension ".js".
The following examples show acceptable filenames for Ajax.org Platform classes:

#
# elements/bar.js
# core/parsers/aml.js
# elements/teleport/rpc/jsonrpc.js
#

  2.2. Functions and Methods
  ==========================

  Function names may only contain alphanumeric characters. The use of
underscores is strongly discouraged, with the notable exception when
declaring a function as pseudo-private. Numbers are permitted in function
names but are discouraged in most cases.

  Function names must always start with a lowercase letter. When a function
name consists of more than one word, the first letter of each new word must be
capitalized. This is commonly called "lower camelCase" formatting[2].

Verbosity is generally encouraged. Function names should be as verbose as is
practical to fully describe their purpose and behavior.

These are examples of acceptable names for functions:

#
# filterInput()
# getElementById()
# widgetFactory()
#

  For object-oriented programming, accessors for instance variables should
always be prefixed with "get" or "set". In implementing design patterns, such
as the singleton or factory patterns, the name of the method should
contain the pattern name where practical to more thoroughly describe behavior.

  For methods on objects that are declared pseudo-private, following general
Javascript scoping rules, the first character of the variable name must be an
underscore. This is the only acceptable application of an underscore in a
method name. Methods declared "public" should never contain an underscore.

  For methods on objects that are declared pseudo-protected, the first character
of the variable name must be a dollar-sign ($). There exists no protected scope
in Javascript, however Ajax.org Platform recognizes the value and use of this
pattern and implements it by using the dollar-sign convention.

  Functions in the global scope (a.k.a. "floating functions") are permitted but
discouraged in most cases. Consider wrapping these functions in the globally
defined 'apf' namespace.

  2.3. Variables
  ==============

  Variable names may only contain alphanumeric characters. Underscores are not
permitted. Numbers are permitted in variable names but are discouraged in most
cases.

  For instance variables that are declared with as "private" or "protected",
the first character of the variable name must be a single underscore. This is
the only acceptable application of an underscore in a variable name. Member
variables declared "public" should never start with an underscore.

  As with function names (see section 2.2) variable names must always start
with a lowercase letter and follow the "camelCaps" capitalization convention[2].

  Verbosity is generally encouraged. Variables should always be as verbose as
practical to describe the data that the developer intends to store in them.
Terse variable names such as "i" and "n" are discouraged for all but the
smallest loop contexts. If a loop contains more than 20 lines of code, the
index variables should have more descriptive names.

  The Hungarian notation[3] for variable names is generally encouraged. Since
Javascript is an untyped language, specifying the variable type as part of the
variable name makes the code much easier to read.

  2.4. Constants
  ==============

  Constants may contain both alphanumeric characters and underscores. Numbers
are permitted in constant names.

  All letters used in a constant name must be capitalized.

  Words in constant names must be separated by underscore characters. For
example, EMBED_SUPPRESS_EMBED_EXCEPTION is permitted but
EMBED_SUPPRESSEMBEDEXCEPTION is not.

  Constants must be defined as class members within its namespace, to avoid 
naming conflicts with other class contants. For example:

#
# apf.bar = apf.component(...);
#
# apf.bar.ALIGN_LEFT = 0; //constant attached to the apf.bar namespace
#

  3. Coding Style
  ===============

  3.1. Strings
  ============

  3.1.1. String Literals
  ======================

  When a string is literal (contains no variable substitutions), the quotation
mark or "double quote" should always be used to demarcate the string:

#
# var a = "Example String";
#

  3.1.2. String Literals Containing Quotation Marks
  =================================================

  When a literal string itself contains quotation marks, it is permitted to
demarcate the string with apostrophes or "single quotes". This is especially
useful for blocks of HTML:

#
# var a = '<div class="button">\
#            <a href="#" title="Click me">Click me</a>\
#          </div>';
#

  This syntax is preferred over escaping quotation marks as it is much easier
to read.

  3.1.3. String Concatenation
  ===========================

  Strings must be concatenated using the "+" operator. A space must always be
added before and after the "+" operator to improve readability:

#
# var sProduct = "Ajax.org" + " " + "Platform";
#

  When concatenating strings with the "+" operator, it is encouraged to break
the statement into multiple lines to improve readability. In these cases, each
successive line should be padded with whitespace such that the "+" operator
is aligned under the "=" operator:

#
# var a = '<div class="button">'
#       + '  <a href="#" title="Click me">Click me</a>'
#       + '</div>';
#

  IMPORTANT: concatenating strings by using the "+" operator has been proven to
be slower in most browsers today than using Arrays:

#
# var a = ['<div class="button">',
#          '  <a href="#" title="Click me">Click me</a>',
#          '</div>'].join('');
#

  Since the speed gain of using this Array technique is only noticable when
concatenating larger strings, it is not recommended for smaller scale string
operations. Using the "+" operator also improves readability of the code.

  3.2. Arrays
  ===========

  3.2.1. Numerically Indexed Arrays
  =================================

  Negative numbers are not permitted as indices.

  An indexed array may start with any non-negative number, however all base
indices besides 0 are discouraged.

  When declaring indexed arrays with the Array construct or "[]" shorthand, a
trailing space must be added after each comma delimiter to improve readability:

#
# var sampleArray = [1, 2, 3, 'Ajax.org', 'Platform'];
#
# var sampleArray2 = new Array(1, 2, 3, 'Ajax.org', 'Platform');
#

  It is permitted to declare multiline indexed arrays using the "Array"
construct or "[]" shorthand. In this case, each successive line must be
padded with spaces such that beginning of each line is aligned:

#
# var sampleArray = [1, 2, 3, 'Ajax.org', 'Platform',
#                    a, b, c,
#                    56.44, d, 500];
#

  3.2.2. Associative Arrays
  =========================

  The Javascript language does not support arrays, but it does support simple
objects to be used in conjuction with the HashTable pattern[4].
  When declaring associative arrays with the "{}" shorthand for simple objects
or collections, breaking the statement into multiple lines is encouraged. In
this case, each successive line must be padded with whitespace such that both
the keys and the values are aligned:

#
# var sampleHash = {
#     'firstKey' : 'firstValue',
#     'secondKey': 'secondValue'
# };
#

  3.3. Classes
  ============

  3.3.1. Class Declaration
  ========================

  Classes must be named according to Ajax.org Platform's naming conventions.

  Every class must be declared inside the "apf" namespace.

  The brace should always be written on the line underneath the class name
(the "one true brace" form).

  Every class must have a documentation block that conforms to the Scriptdoc
standard.

  All code in a class must be indented with four spaces.

  Only one class is permitted in each Javascript file.

  Placing additional code in class files is permitted but discouraged. In such
files, two blank lines must separate the class from any additional Javascript
code in the class file.

  The following is an example of an acceptable class declaration:

#
# /**
#  * Documentation Block Here
#  */
# apf.sampleClass = function() {
#     // all contents of class
#     // must be indented four spaces
# }
#

  3.3.2. Class Member Variables
  =============================

  Member variables must be named according to Ajax.org Platform's variable
naming conventions.

  Any variables declared in a class must be listed at the top of the class,
above the declaration of any methods.

  Giving access to member variables directly by declaring them as public is
permitted but discouraged in favor of accessor methods (set/get).

  3.4. Functions and Methods
  ==========================

  3.4.1. Function and Method Declaration
  ======================================

  Functions must be named according to the Ajax.org Platform's function naming
conventions.

  As with classes, the brace should always be written on the same line as the
function name. Space between the function name and the opening parenthesis for
the arguments is not permitted.

  Functions in the global scope are strongly discouraged.

  The following is an example of an acceptable function declaration in a class:

#
# /**
#  * Documentation Block Here
#  */
# apf.foo = function() {
#     /**
#      * Documentation Block Here
#      */
#     this.bar = function() {
#         // all contents of function
#         // must be indented four spaces
#     }
# }
#

  3.4.2. Function and Method Usage
  ================================

  Function arguments should be separated by a single trailing space after the
comma delimiter. The following is an example of an acceptable invocation of a
function that takes three arguments:

#
# threeArguments(1, 2, 3);
#

  In passing arrays as arguments to a function, the function call may include
the "[]" or "{}" shorthands and may be split into multiple lines to improve
readability. In such cases, the normal guidelines for writing arrays still
apply:

#
# threeArguments([1, 2, 3], 2, 3);
#
# threeArguments([1, 2, 3, 'Ajax.org', 'Platform',
#                 a, b, c,
#                 56.44, $d, 500], 2, 3);
#

  3.5. Control Statements
  =======================

  3.5.1. If/Else/Else If
  ======================

  Control statements based on the if and else if constructs must have a single
space before the opening parenthesis of the conditional and a single space
after the closing parenthesis.

  Within the conditional statements between the parentheses, operators must be
separated by spaces for readability. Inner parentheses are encouraged to improve
logical grouping for larger conditional expressions.

  The opening brace is written on the same line as the conditional statement.
The closing brace is always written on its own line. Any content within the
braces must be indented using four spaces.

#
# if ($a != 2) {
#     $a = 2;
# }
#

  For "if" statements that include "else if" or "else", the formatting
conventions are similar to the "if" construct. The following examples
demonstrate proper formatting for "if" statements with "else" and/or "else if"
constructs:

#
# if (a != 2) {
#     a = 2;
# } else {
#    a = 7;
# }
#

  Note: the "else" and "else if" constructs may be written on its own line, as
the following example demonstrates:

#
# if (a != 2) {
#     a = 2;
# }
# else if (a == 3) {
#    a = 4;
# }
# else {
#    a = 7;
# }
#

  Javascript allows statements to be written without braces in some
circumstances. This coding standard allows the following cases:

#
# // the 'quick escape' case:
# if (!a) return;
#
# // the 'oneliner' case:
# if (!a)
#     this.foo();
# else
#     this.bar();
#

  Javascript provides a shorthand statement for the "if...else" sequence. This
coding standard allows the following formats:

#
# // On one line, if it doesn't exceed the limit of 80 characters in length
# var a = b ? b + 10 : 200;
#
# // On multiple lines, to improve readability:
# var a = (value > 20 && otherValue < 10 && boolFoo === false)
#     ? this.foo();
#     : this.bar();
#

  3.5.2. Switch
  =============

  Control statements written with the "switch" statement must have a single
space before the opening parenthesis of the conditional statement and after the
closing parenthesis.

  All content within the "switch" statement must be indented using four spaces.
Content under each "case" statement must be indented using an additional
four spaces.

#
# switch (numPeople) {
#     case 1:
#         break;
#
#     case 2:
#         break;
#
#     default:
#         break;
# }
#

  The construct default should never be omitted from a switch statement.

  NOTE: It is sometimes useful to write a case statement which falls through
to the next case by not including a break or return within that case. To
distinguish these cases from bugs, any case statement where break or return are
omitted should contain a comment indicating that the break was intentionally
omitted.

  3.5.3 For Loop
  ==============

  Control statements written with the "for" statement must have a single
space before the opening parenthesis of the initialization clause and after the
closing parenthesis.

  Each clause of the "for" statement should be followed by one space to mark
the end of the clause and the start of the following one.

  All content within the "for" statement must be indented using four spaces.

#
# for (initialization; condition; update) {
#     statement;
# }
#
# // Example:
# for (var i = 0; i < j; i++) {
#     this.foo();
# }
#

  When using the comma operator in the initialization or update clause of a
"for" statement, avoid the complexity of using more than three variables. If
needed, use separate statements before the for loop (for the initialization
clause) or at the end of the loop (for the update clause).

  Javascript allows statements to be written without braces in some
circumstances. This coding standard makes no differentiation - all "for"
statements must use braces.

  3.5.4 While/Do While Loop
  =========================

  Control statements written with the "while" and "do while" statement must
have a single space before the opening parenthesis of the condition clause
and after the closing parenthesis.

  The "while" clause of a "do while" statement must be written on its own line,
to improve readability of the code.

#
# while (condition) {
#     statement;
# }
#
# do {
#     statement;
# }
# while (condition);
#
# // Example:
# var i = 10;
# while (i >= 10) {
#     this.foo(i);
#     i--;
# }
#

  3.5.5 Try Catch
  ===============

  The "try" keyword of a "try catch" statement must have a single space before
the opening inner parenthesis.

  The "catch" clause of a "try catch" statement must be written on it's own line
and have a single space before the opening parenthesis of the initialization
clause and after the closing parenthesis.

  A "try catch" statement may also be followed by the "finally" keyword, which
executes regardless of whether or not the try block has completed successfully.

#
# try {
#     statements;
# }
# catch (e) {
#     statements;
# }
# finally {
#     statements;
# }
#

  3.6. Inline Documentation
  =========================

  3.6.1. Documentation Format
  ===========================

  All documentation blocks ("docblocks") must be compatible with the
Scriptdoc[5] format. Describing the Scriptdoc format is beyond the scope of
this document. For more information, visit: http://scriptdoc.org/

  All class files must contain a "file-level" docblock at the top of each file
and a "class-level" docblock immediately above each class. Examples of such
docblocks can be found below.

  3.6.2. Files
  ============

  Every file that contains Javascript code must have a docblock at the top of
the file, just below the license block, as described in section 1.1, that
contains these Scriptdoc tags at a minimum:

#
# /**
#  * Short description for file
#  *
#  * Long description for file (if any)...
#  *
#  * @copyright  2008 Ajax.org [Optional]
#  * @version    $Id:$
#  * @link       http://api.ajax.org/package/PackageName
#  * @since      1.0
#  */
#

  3.6.3. Classes
  ==============

  Every class must have a docblock that contains these Scriptdoc tags at a
minimum:

#
# /**
#  * Short description for class
#  *
#  * Long description for class (if any)...
#  *
#  * @copyright  2008 Ajax.org [Optional]
#  * @version    Release: @package_version@
#  * @link       http://api.ajax.org/package/PackageName
#  * @since      0.8
#  * @deprecated Class deprecated in Release 1.0
#  */
#

  3.6.4. Functions
  ================

  Every function, including object methods, must have a docblock that contains
at a minimum:

  * A description of the function
  * All of the arguments
  * All of the possible return values

  It is recommended to use the "@access" tag because the access level is
not known from following the general Javascript scoping rules. Use the
"@private" and "@protected" modifiers to document functions that are not
publicly accessible.

  If a function/ method may throw an exception, use @throws for all known
exception types:

#
# @throws exceptionclass [description]
#

  A. Links
  ========

[1] We are using O3 as a Javascript compiler/ pre-processor.
    See http://www.ajax.org/#o3 for more information
[2] http://en.wikipedia.org/wiki/Camelcase#Current_usage_in_computing - Wikipedia 
    entry for camelCase usage in computing
[3] http://en.wikipedia.org/wiki/Hungarian_notation - Wikipedia entry for 
    Hungarian notation
[4] http://en.wikipedia.org/wiki/Hashmap - Wikipedia entry for Hash Table
[5] http://scriptdoc.org/ - Scriptdoc standards home
[6] http://www.gnu.org/software/womb/gnits/ - Gnits standards