Firebug Coding Style

From FirebugWiki

(Difference between revisions)
Jump to: navigation, search
(Changed code blocks to use syntax highlighting)
m (Abbriviations in variable names should never be a single character)
(34 intermediate revisions not shown)
Line 1: Line 1:
-
This document attempts to explain the basic styles and patterns, that are used in Firebug codebase. New code should try to conform to these standards, so that it is as easy to maintain as existing code. Of course every rule has an exception, but it's important to know the rules nonetheless!
+
This document attempts to explain the basic styles and patterns, that are used in the Firebug codebase. New code should try to conform to these standards, so that it is as easy to maintain as existing code. Of course every rule has an exception, but it's important to know the rules nonetheless!
-
 
+
-
== Resources ==
+
-
 
+
-
* [http://getfirebug.com/wiki/index.php/Firebug_Source_Code_Comments Firebug Source Code Comments]
+
-
* [https://developer.mozilla.org/en/JavaScript_Tips Mozilla JavaScript Tips]
+
-
* [https://developer.mozilla.org/En/Developer_Guide/Coding_Style Mozilla Coding Style]
+
== Formatting Code ==
== Formatting Code ==
 +
=== File Encoding ===
 +
All source files should be encoded in UTF-8 without [http://en.wikipedia.org/wiki/Byte_order_mark BOM].
=== Whitespace ===
=== Whitespace ===
-
No tabs. No whitespace at the end of a line.
+
No tabs. No whitespace at the end of a line. But, every line should end with Unix line break, i.e. a line feed character (<code>\n</code>, Unicode: <code>0x0A</code>), also the last line of a file.
 +
 
 +
Operators are surrounded by spaces as well as parameters in a function call.
 +
 
 +
<source lang="javascript">
 +
var text = "Message: " + msgID + ": " + msgText;
 +
var result = result ? "positive" : "negative";
 +
var target = event.target || document.getElementsByTagName("body")[0];
 +
var expression = getExpressionAt(rangeParent.data, rangeOffset);
 +
</source>
 +
 
 +
The incrementation and decrementation operators are not separated by spaces. So e.g. you should write <code>while(i-- > 0)</code> instead of <code>while(i --> 0)</code> to avoid misinterpretations.
 +
 
 +
=== Source File Size ===
 +
A source file should avoid huge amount of code lines. Couple thousands of lines in a file is already a lot. Firebug is using [http://wiki.commonjs.org/wiki/Modules/AsynchronousDefinition AMD syntax] and more smaller files (modules) is preferred.
=== Line Length ===
=== Line Length ===
-
100 characters or less.
+
100 characters or less. There is no exception in <code>*.js</code> files! In some cases this rule can be broken in <code>*.html</code> or <code>*.xul</code> files. But keep in mind long lines are hard to read (also search results are hard to read).
-
There is no exception is <code>*.js</code> files! In some cases this rule can be broken in <code>*.html</code> or <code>*.xul</code> files. But keep in mind long lines are hard to read (also search results are hared to read).
+
 
 +
When wrapping lines, operators stay at the end of a line.
 +
<source lang="javascript">
 +
if ((... &&
 +
    ...) ||
 +
    ...)
 +
{
 +
}
 +
</source>
 +
 
 +
<source lang="javascript">
 +
var string = ... +
 +
    ...;
 +
</source>
 +
 
 +
Also member operators stay at the end of the line.
 +
 
 +
<source lang="javascript">
 +
var service = Cc[...].
 +
    getService(...);
 +
</source>
=== Indentation ===  
=== Indentation ===  
Four spaces per logic level.
Four spaces per logic level.
-
=== Licence ===
+
=== Commands ===
 +
Every command must end with a semicolon and must be on its own line.
 +
 
 +
<source lang="javascript">
 +
var foo = 1;
 +
var bar = 2;
 +
 
 +
foo = someFunction();
 +
 
 +
bar += 3;
 +
return bar;
 +
</source>
 +
 
 +
=== License ===
Files should include a license note at the first line of the file:
Files should include a license note at the first line of the file:
Line 27: Line 70:
</source>
</source>
-
In case of a XML files (e.g. in overlays), this must be after XML declaration, for example:
+
In case of <code>*.xml</code> files (e.g. in overlays), this must be after XML declaration, for example:
<source lang="xml">
<source lang="xml">
<?xml version="1.0"?>
<?xml version="1.0"?>
Line 35: Line 78:
</source>
</source>
-
In case of a *.properties or *.manifest files, this must be commented using # character.
+
In case of <code>*.properties</code> or <code>*.manifest</code> files, this must be commented using # character.
<source lang="properties">
<source lang="properties">
# See license.txt for terms of usage
# See license.txt for terms of usage
Line 42: Line 85:
=== Control Structures ===
=== Control Structures ===
-
Existing Firebug codebase uses braces on the next line, like as follows:
+
Existing Firebug codebase uses braces on the next line like as follows:
<source lang="javascript">
<source lang="javascript">
Line 51: Line 94:
</source>
</source>
-
Yes, there can be exceptions and K&R style can be preferred in some cases. For example, definition of a config object.
+
Yes, there can be exceptions and [http://en.wikipedia.org/wiki/The_C_Programming_Language_%28book%29 K&R] style can be preferred in some cases. For example, definition of a config object.
<source lang="javascript">
<source lang="javascript">
Line 62: Line 105:
</source>
</source>
-
Anyway, class and functions definitions should always have the braces on the next line as follows:
+
Anyway, class and function definitions should always have the braces on the next line as follows:
<source lang="javascript">
<source lang="javascript">
Line 80: Line 123:
</source>
</source>
-
Control structures should look like as follows (also notice the spacing between a keyword and left bracket):
+
Control structures should look like as follows (also notice the spacing between a keyword and the left bracket):
<source lang="javascript">
<source lang="javascript">
Line 103: Line 146:
{
{
     case 1:
     case 1:
-
     {
+
        ...
-
     }
+
        break;
 +
 
 +
     case 2:
 +
        ...
 +
        break;
 +
 
 +
     default:
 +
        ...
}
}
</source>
</source>
 +
 +
Ternary expressions must be wrapped in brackets for clarity.
 +
 +
<source lang="javascript">
 +
var variable = (condition ? true : false);
 +
</source>
 +
 +
To avoid misunderstandings ''for'' loops are always written in their long form, i.e. loop heads like <code>for (var i = count; i--; )</code> should be avoided in favor of <code>for (var i = count-1; i>=0; i--)</code>. Also there are spaces between the statements and you should write <code>i++</code> instead of <code>++i</code>.
<source lang="javascript">
<source lang="javascript">
-
for (var i=0; i<10; i++)
+
for (var i = 0; i < 10; i++)
{
{
}
}
Line 123: Line 181:
</source>
</source>
-
Firebug prefers no braces if they are not necessary.
+
Firebug prefers no braces, if they are not necessary.
<source lang="javascript">
<source lang="javascript">
Line 132: Line 190:
</source>
</source>
-
But if one of the branches needs braces use them for all:
+
But if one of the branches needs braces use them for all. Also note
<source lang="javascript">
<source lang="javascript">
if (...)
if (...)
Line 143: Line 201:
     dump(2);
     dump(2);
}
}
 +
</source>
 +
 +
If the head of a control structure is wrapped into several lines because it is longer than the maximum line length, also use braces, even when the block just contains one line.
 +
<source lang="javascript">
 +
if (...
 +
    ...)
 +
{
 +
    dump("0");
 +
}
 +
else
 +
{
 +
    dump(2);
 +
}
 +
</source>
 +
 +
Firebug prefers no brackets for operators like <code>typeof</code>.
 +
 +
<source lang="javascript">
 +
if (typeof variable == "object")
 +
    return false;
 +
</source>
 +
 +
=== Comments ===
 +
Multi-line as well as single line comments should always be put into their own line.
 +
So you should write:
 +
 +
<source lang="javascript">
 +
// This is a comment
 +
var abc = xyz;
 +
</source>
 +
 +
Comments for blocks of code will be placed above them.
 +
 +
<source lang="javascript">
 +
if (foo == "bar")
 +
{
 +
    ...
 +
}
 +
// foo is not set to "bar"
 +
else
 +
{
 +
    ...
 +
}
 +
</source>
 +
 +
To describe what specific functions do, especially published APIs, [http://en.wikipedia.org/wiki/JSDoc JSDoc] comments are used.
 +
 +
<source lang="javascript">
 +
/**
 +
* Returns the domain of a given URL
 +
*
 +
* @param {string} url URL, for which to get the domain
 +
*
 +
* @return {string} Domain
 +
*/
 +
Url.getDomain = function(url)
 +
{
 +
    var m = /[^:]+:\/{1,3}([^\/]+)/.exec(url);
 +
    return m ? m[1] : "";
 +
};
</source>
</source>
=== Horizontal Lines ===
=== Horizontal Lines ===
-
Sometimes is helpful to divide portions of a file by a horizontal line. For this, you should use following comment (100 characters long):
+
Sometimes it is helpful to divide portions of a file by a horizontal line. For this you should use following comment (100 characters long):
<source lang="javascript">
<source lang="javascript">
Line 153: Line 271:
</source>
</source>
-
Firebug codebase also uses following horizontal separator for dividing members of one object (this separator uses indentation (4 spaces) since it's used within an object scope that is indented (100 characters long).
+
Firebug codebase also uses the following horizontal separator for dividing members of one object (this separator uses indentation (4 spaces) since it's used within an object scope that is indented (100 characters long).
<source lang="javascript">
<source lang="javascript">
Line 160: Line 278:
== Naming ==
== Naming ==
 +
 +
American English is used for all labels and comments. That means, that you should write e.g. <code>synchronize</code> instead of <code>synchronise</code> or <code>color</code> instead of <code>colour</code>.
=== Functions and Methods ===
=== Functions and Methods ===
-
Functions should use camelCase but should not capitalize the first letter.
+
Functions should use camelCase but should not capitalize the first letter. Also functions names must start with a verb.
<source lang="javascript">
<source lang="javascript">
-
function foo()
+
function initialize()
{
{
}
}
Line 171: Line 291:
<source lang="javascript">
<source lang="javascript">
-
function myFoo()
+
function getLocationList()
{
{
}
}
Line 177: Line 297:
=== Objects ===
=== Objects ===
-
Constructors for objects should be capitalized and use CamelCase
+
Constructors for objects should be capitalized and use CamelCase.
<source lang="javascript">
<source lang="javascript">
Line 201: Line 321:
=== Constants ===
=== Constants ===
-
Constants should be capitalized as follows
+
Constants should be capitalized as follows:
<source lang="javascript">
<source lang="javascript">
Line 207: Line 327:
</source>
</source>
-
Use <code>var</code> instead of <code>const</code> since the code can be also used in browser environment where ''const'' is not supported.
+
Use <code>var</code> instead of <code>const</code>, since the code can also be used in the browser environment where ''const'' is not supported.
=== Variables ===
=== Variables ===
-
Variable should use camelCase and not capitalize the first letter.
+
Variables should use camelCase and not capitalize the first letter. Variable definitions should be done separately, not comma-separated. They don't have to be initialized immediately but before they are used.
 +
If abbreviations are used, they should be written lower case at the beginning of a variable but in capitals when they are in the middle of the name. Also they should not be a single character.
<source lang="javascript">
<source lang="javascript">
-
var thisIsMyVariable = true;
+
var myFirstVariable = true;
 +
var mySecondVariable = false;
 +
var url = "http://getfirebug.com/wiki";
 +
var baseURL = "http://getfirebug.com/";
</source>
</source>
Line 222: Line 346:
=== Vertical Indentation ===
=== Vertical Indentation ===
-
Method defintions should be separated by a new line. Note the new line between ''initialize'' and ''shutdown'' methods.
+
Method defintions should be separated by a new line. Note the new line between ''initialize'' and ''shutdown'' methods.
<source lang="javascript">
<source lang="javascript">
Line 262: Line 386:
{
{
}
}
 +
</source>
 +
 +
=== Strict Mode ===
 +
 +
Source files should include a "use strict"; directive below the AMD imports separated by an empty line before and after it:
 +
 +
<source lang="javascript">
 +
/* See license.txt for terms of usage */
 +
 +
define([
 +
    "firebug/firebug",
 +
    "firebug/domplate"
 +
],
 +
function(Firebug, Domplate) {
 +
 +
"use strict";
 +
 +
// ...
 +
 +
});
</source>
</source>
Line 306: Line 450:
</source>
</source>
-
The code should also have [http://getfirebug.com/wiki/index.php/Firebug_Source_Code_Comments comments].
+
The code should also have [[Firebug Source Code Comments|comments]].
-
== Example Module File (AMD)==
+
== Example Module File ==
-
Example of a typical asynchronous module definition. Every file in Firebug source base should use AMD pattern since Firebug 1.8
+
Example of a typical [http://wiki.commonjs.org/wiki/Modules/AsynchronousDefinition asynchronous module definition (AMD)]. Every file in Firebug source base should use the AMD pattern starting from Firebug 1.8.
<source lang="javascript">
<source lang="javascript">
Line 315: Line 459:
define([
define([
-
    "firebug/lib",
 
     "firebug/firebug",
     "firebug/firebug",
 +
    "firebug/lib/object",
     "firebug/domplate"
     "firebug/domplate"
],
],
-
function(FBL, Firebug, Domplate) {
+
function(Firebug, Obj, Domplate) {
 +
 
 +
"use strict";
// ********************************************************************************************* //
// ********************************************************************************************* //
Line 329: Line 475:
// Module Implementation
// Module Implementation
-
Firebug.MyModule = extend(Firebug.Module,
+
Firebug.MyModule = Obj.extend(Firebug.Module,
{
{
     // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
     // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Line 357: Line 503:
</source>
</source>
-
The code should also have [http://getfirebug.com/wiki/index.php/Firebug_Source_Code_Comments comments].
+
The code should also have [[Firebug Source Code Comments|comments]].
 +
 
 +
== Resources ==
 +
* [https://github.com/fflorent/firebug_vimrc/ vimrc file] supporting Firebug coding style.  
 +
 
 +
== See also ==
 +
* [[Firebug Modules]]
 +
* [[Firebug Source Code Comments]]
 +
* [https://developer.mozilla.org/en/JavaScript_Tips Mozilla JavaScript Tips]
 +
* [https://developer.mozilla.org/en/Developer_Guide/Coding_Style Mozilla Coding Style]

Revision as of 18:46, 24 September 2013

This document attempts to explain the basic styles and patterns, that are used in the Firebug codebase. New code should try to conform to these standards, so that it is as easy to maintain as existing code. Of course every rule has an exception, but it's important to know the rules nonetheless!

Contents

Formatting Code

File Encoding

All source files should be encoded in UTF-8 without BOM.

Whitespace

No tabs. No whitespace at the end of a line. But, every line should end with Unix line break, i.e. a line feed character (\n, Unicode: 0x0A), also the last line of a file.

Operators are surrounded by spaces as well as parameters in a function call.

var text = "Message: " + msgID + ": " + msgText;
var result = result ? "positive" : "negative";
var target = event.target || document.getElementsByTagName("body")[0];
var expression = getExpressionAt(rangeParent.data, rangeOffset);

The incrementation and decrementation operators are not separated by spaces. So e.g. you should write while(i-- > 0) instead of while(i --> 0) to avoid misinterpretations.

Source File Size

A source file should avoid huge amount of code lines. Couple thousands of lines in a file is already a lot. Firebug is using AMD syntax and more smaller files (modules) is preferred.

Line Length

100 characters or less. There is no exception in *.js files! In some cases this rule can be broken in *.html or *.xul files. But keep in mind long lines are hard to read (also search results are hard to read).

When wrapping lines, operators stay at the end of a line.

if ((... &&
    ...) ||
    ...)
{
}
var string = ... +
    ...;

Also member operators stay at the end of the line.

var service = Cc[...].
    getService(...);

Indentation

Four spaces per logic level.

Commands

Every command must end with a semicolon and must be on its own line.

var foo = 1;
var bar = 2;
 
foo = someFunction();
 
bar += 3;
return bar;

License

Files should include a license note at the first line of the file:

/* See license.txt for terms of usage */
...

In case of *.xml files (e.g. in overlays), this must be after XML declaration, for example:

<?xml version="1.0"?>
<!-- See license.txt for terms of usage -->
...
</xml>

In case of *.properties or *.manifest files, this must be commented using # character.

# See license.txt for terms of usage
...

Control Structures

Existing Firebug codebase uses braces on the next line like as follows:

function foo()
{
    // ...
}

Yes, there can be exceptions and K&R style can be preferred in some cases. For example, definition of a config object.

var foo = { prop1: "value1" };
 
var bar = {
    prop1: "value1",
    prop2: "value2",
};

Anyway, class and function definitions should always have the braces on the next line as follows:

Firebug.MyModule = extend(Firebug.Module,
{
    initializeUI: function()
    {
    },
});
function myFunction()
{
    // ....
}

Control structures should look like as follows (also notice the spacing between a keyword and the left bracket):

if (...)
{
}
else if (...)
{
}

Another example showing how to deal with spaces:

if ((a > 0) && (b > 0))
{
}
switch (...)
{
    case 1:
        ...
        break;
 
    case 2:
        ...
        break;
 
    default:
        ...
}

Ternary expressions must be wrapped in brackets for clarity.

var variable = (condition ? true : false);

To avoid misunderstandings for loops are always written in their long form, i.e. loop heads like for (var i = count; i--; ) should be avoided in favor of for (var i = count-1; i>=0; i--). Also there are spaces between the statements and you should write i++ instead of ++i.

for (var i = 0; i < 10; i++)
{
}
try
{
}
catch (err)
{
}

Firebug prefers no braces, if they are not necessary.

if (...)
    dump(true);
else
    dump(false);

But if one of the branches needs braces use them for all. Also note

if (...)
{
    dump("0");
    dump("1");
}
else
{
    dump(2);
}

If the head of a control structure is wrapped into several lines because it is longer than the maximum line length, also use braces, even when the block just contains one line.

if (...
    ...)
{
    dump("0");
}
else
{
    dump(2);
}

Firebug prefers no brackets for operators like typeof.

if (typeof variable == "object")
    return false;

Comments

Multi-line as well as single line comments should always be put into their own line. So you should write:

// This is a comment
var abc = xyz;

Comments for blocks of code will be placed above them.

if (foo == "bar")
{
    ...
}
// foo is not set to "bar"
else
{
    ...
}

To describe what specific functions do, especially published APIs, JSDoc comments are used.

/**
 * Returns the domain of a given URL
 * 
 * @param {string} url URL, for which to get the domain
 * 
 * @return {string} Domain
 */
Url.getDomain = function(url)
{
    var m = /[^:]+:\/{1,3}([^\/]+)/.exec(url);
    return m ? m[1] : "";
};

Horizontal Lines

Sometimes it is helpful to divide portions of a file by a horizontal line. For this you should use following comment (100 characters long):

// ********************************************************************************************* //

Firebug codebase also uses the following horizontal separator for dividing members of one object (this separator uses indentation (4 spaces) since it's used within an object scope that is indented (100 characters long).

    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

Naming

American English is used for all labels and comments. That means, that you should write e.g. synchronize instead of synchronise or color instead of colour.

Functions and Methods

Functions should use camelCase but should not capitalize the first letter. Also functions names must start with a verb.

function initialize()
{
}
function getLocationList()
{
}

Objects

Constructors for objects should be capitalized and use CamelCase.

function ObjectConstructor()
{
}
Firebug.MyModule = extend(Firebug.Module,
{
});
MyObject.prototype = ()
{
    myMethod: function()
    {
    }
};

Constants

Constants should be capitalized as follows:

var MY_CONSTANT = true;

Use var instead of const, since the code can also be used in the browser environment where const is not supported.

Variables

Variables should use camelCase and not capitalize the first letter. Variable definitions should be done separately, not comma-separated. They don't have to be initialized immediately but before they are used. If abbreviations are used, they should be written lower case at the beginning of a variable but in capitals when they are in the middle of the name. Also they should not be a single character.

var myFirstVariable = true;
var mySecondVariable = false;
var url = "http://getfirebug.com/wiki";
var baseURL = "http://getfirebug.com/";

Prefixes

Firebug codebase doesn't use any prefixes for member fields.

Good Practices

Vertical Indentation

Method defintions should be separated by a new line. Note the new line between initialize and shutdown methods.

Firebug.MyModule = extend(Firebug.Module,
{
    initialize: function()
    {
    },
 
    shutdown: function()
    {
    }
});

Also portions of code logically belonging together should be separated by a new line from other code. Note the new line between super.initialize and this.onMutateText.

initialize: function()
{
    super.initialize.apply(this, arguments);
 
    this.onMutateText = bind(this.onMutateText, this);
    this.onMutateAttr = bind(this.onMutateAttr, this);
    this.onMutateNode = bind(this.onMutateNode, this);
}

Horizontal lines should be surrounded by new lines too

function myFunc1()
{
}
 
// ********************************************************************************************* //
 
function myFunc2()
{
}

Strict Mode

Source files should include a "use strict"; directive below the AMD imports separated by an empty line before and after it:

/* See license.txt for terms of usage */
 
define([
    "firebug/firebug",
    "firebug/domplate"
],
function(Firebug, Domplate) {
 
"use strict";
 
// ...
 
});

Example File

Example of a typical Firebug file implementing a module object. Firebug namespaces (FBL.ns) are no longer the preferred way for Firebug files. See AMD below.

/* See license.txt for terms of usage */
 
FBL.ns(function() {
 
// ********************************************************************************************* //
// Constants
 
var MY_CONSTANT = true;
 
// ********************************************************************************************* //
// Module Implementation
 
Firebug.MyModule = extend(Firebug.Module,
{
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    // Initialization
 
    initializeUI: function()
    {
    },
 
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    // Toolbar Actions
 
    myButtonHandler: function()
    {
    }
});
 
// ********************************************************************************************* //
// Registration
 
Firebug.registerModule(Firebug.StartButton);
 
// ********************************************************************************************* //
});

The code should also have comments.

Example Module File

Example of a typical asynchronous module definition (AMD). Every file in Firebug source base should use the AMD pattern starting from Firebug 1.8.

/* See license.txt for terms of usage */
 
define([
    "firebug/firebug",
    "firebug/lib/object",
    "firebug/domplate"
],
function(Firebug, Obj, Domplate) {
 
"use strict";
 
// ********************************************************************************************* //
// Constants
 
var MY_CONSTANT = true;
 
// ********************************************************************************************* //
// Module Implementation
 
Firebug.MyModule = Obj.extend(Firebug.Module,
{
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    // Initialization
 
    initializeUI: function()
    {
    },
 
    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
    // Toolbar Actions
 
    myButtonHandler: function()
    {
    }
});
 
// ********************************************************************************************* //
// Registration
 
Firebug.registerModule(Firebug.MyModule);
 
return Firebug.MyModule;
 
// ********************************************************************************************* //
});

The code should also have comments.

Resources

See also

Personal tools