Firebug Coding Style

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No tabs. No whitespace at the end of a line. But, every line should end with a line feed character (<code>\n</code>, Unicode: <code>0x0A</code>), also the last line of a file.
No tabs. No whitespace at the end of a line. But, every line should end with 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, except the string concatinator.
+
Operators are surrounded by spaces as well as parameters in a function call.
<source lang="javascript">
<source lang="javascript">
-
var text = "Message: "+msgID+": "+msgText;
+
var text = "Message: " + msgID + ": " + msgText;
var result = result ? "positive" : "negative";
var result = result ? "positive" : "negative";
var target = event.target || document.getElementsByTagName("body")[0];
var target = event.target || document.getElementsByTagName("body")[0];
Line 368: Line 368:
}
}
</source>
</source>
 +
 +
=== Strict Mode ===
 +
 +
Source files (at least new ones) should include a "use strict"; directive below the AMD imports:
 +
 +
<source lang="javascript">
 +
/* See license.txt for terms of usage */
 +
 +
define([
 +
    "firebug/firebug",
 +
    "firebug/domplate"
 +
],
 +
function(Firebug, D) {
 +
"use strict";
 +
 +
// ...
 +
 +
});
 +
</source>
 +
 +
Note that "with" can not be used in strict mode, so any domplate template will have to include explicit "<code>D.</code>"s before each tag.
== Example File ==
== Example File ==

Revision as of 00:29, 5 February 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 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.

Variable definitions should be done separately, not comma-separated.

var foo = 1;
var bar = 2;
 
foo = someFunction();

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--)

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;

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.

function foo()
{
}
function myFoo()
{
}

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.

var thisIsMyVariable = true;

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 (at least new ones) should include a "use strict"; directive below the AMD imports:

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

Note that "with" can not be used in strict mode, so any domplate template will have to include explicit "D."s before each tag.

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/lib",
    "firebug/firebug",
    "firebug/domplate"
],
function(FBL, Firebug, Domplate) {
 
// ********************************************************************************************* //
// Constants
 
var MY_CONSTANT = true;
 
// ********************************************************************************************* //
// Module Implementation
 
Firebug.MyModule = 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

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