JSCocoa, a bridge from Javascript to Cocoa

JSCocoa lets you use Cocoa in Javascript. You can write Cocoa applications (almost) entirely in Javascript, or use it as a Plugin engine, like Acorn does. JSCocoa uses WebKit's Javascript framework, JavascriptCore.

JSCocoa is a way to use Cocoa from a Mac desktop app or from the iPhone simulator. (iPhone coming up after I implement Tim Burk's method pool to sidestep iPhone's disabled mprotect). It works just like other bridges :

• RubyCocoa, MacRuby write Cocoa in Ruby
• PyObjC write Cocoa in Python
• LuaCore write Cocoa in Lua

JSCocoa isn't a Javascript framework to use on the Web. For that, check out :

• Cappuccino an open source framework that makes it easy to build desktop-caliber applications that run in a web browser
• SproutCore makes building javascript applications fun and easy

Contribute and discuss

• Discussion group Questions ? Join the Google group and ask away !
• Twitter Tweet me questions and comments
• Github fork JSCocoa from Github, add changes, and notify me with a pull request
• Documentation on Google Code

Who uses it ?

• Narwhal-jsc A JavascriptCore + optional JSCocoa module for Narwhal (Server-side Javascript)
• JSCocoaLoader-sugar JSCocoaLoader.sugar allows the Espresso text editor to be extended using JSCocoa
• JSTalk Gus Mueller, to let Cocoa applications be scripted in Javascript
• PluginManager Grayson Hansard wrote a manager that enables you to write Cocoa plugins in AppleScript, F-Script, Javascript, Lua, Nu, Python and Ruby.
• Elysium Matt Mower, to script Elysium, a MIDI sequencer
• Acorn Plugins Gus Mueller, to let Acorn users write Acorn plugins in Javascript
• Interactive console for iPhone Kumagai Kentaro wrote a console to interact with the iPhone simulator from a web page !
• JSCocoaCodaLoader write Javascript plugins that work in Coda
• REPL console Tom Robinson's command line interface

Are you missing on that list ? Send me a mail !

What does it look like ?

Use straight Javascript syntax to call Cocoa.

// Get current application name
var appName = NSWorkspace.sharedWorkspace.activeApplication.NSApplicationName

// Alloc an object (need to release)
var button = NSButton.alloc.initWithFrame(NSMakeRect(0, 0, 100, 40))
// Alloc an object (no need to release)
var button = NSButton.instance({ withFrame:NSMakeRect(0, 0, 100, 40) }) 

// Setting
var window = NSWorkspace.sharedWorkspace.activeApplication.keyWindow
// Instead of calling setTitle ...
window.setTitle('new title')
// ... set the 'title' property
window.title = 'new title'

// Call methods with jQuery-like syntax
obj.call({ withParam1:'Hello', andParam2:'World' }) 
obj['callWithParam1:andParam2:']('Hello', 'World') 
obj.callWithParam1_andParam2('Hello', 'World' )

// Unicode identifiers !
function	追加する(最初の, 次の)	{	return 最初の+ 次の }
var 結果 = 追加する('こんにちは', '世界')
NSApplication.sharedApplication.keyWindow.title = 結果

// Define a new Javascript class usable by Cocoa (inspired by Cappucino)
class MyClass < NSObject
{
	// Custom drawing, calling parent method
	- (void)drawRect:(NSRect)rect
	{
		// do some drawing here
		...
		// Call parent method
		this.Super(arguments)			
	}
	// Class method
	+ (float)addFloatX:(float)x andFloatY:(float)y
	{
		return x + y
	}
}

// Manipulate an existing class
class NSButton
{
	// Add a method to an existing class
	- (void)someNewMethod:(NSString*)name
	{
		...
	}

	// Swizzle an instance method of an existing class
	Swizzle- (void)drawRect:(NSRect)rect
	{
		// Draw something behind the button
		...
		// Call original swizzled method
		this.Original(arguments)
		// Draw something in front of the button
		NSBezierPath.bezierPathWithOvalInRect(rect).stroke
	}
}

Starting up

This will start a controller, eval a file, call a Javascript method and get an ObjC object out of it. You can start multiple interpreters, e.g. one for each document.

// Start
JSCocoa* jsc = [JSCocoa new];

// Eval a file
[jsc evalJSFile:@"path to a file"];
// Eval a string
[jsc evalJSString:@"log(NSWorkspace.sharedWorkspace.activeApplication.NSApplicationName)"];

// Add an object of ours to the Javascript context
[jsc setObject:self withName:@"controller"];

// Call a Javascript method - we can use any object we added with setObject
JSValueRef returnValue = [jsc callJSFunctionNamed:@"myJavascriptFunction" withArguments:self, nil];
// The return value might be a raw Javascript value (null, true, false, a number) or an ObjC object
// To get an ObjC object
id resultingObject = [jsc unboxJSValueRef:returnValue];

// (Cleanup : only needed if you don't use ObjC's Garbage Collection)
[jsc release];

Add it to your project

Going the framework route :

• Build JSCocoa/JSCocoa.xcodeproj
• Add built JSCocoa.framework to your project
• import <JSCocoa/JSCocoa.h>

No framework, adding JSCocoa files into your project :

• Drag the JSCocoa folder in your project
• Delete irrelevant files (Info.plist, JSCocoa_Prefix.pch, English.lproj, project files)
• Add the JavascriptCore framework
• In 'Build' project settings, add -lffi to 'Other linker flags'
• import "JSCocoa.h"

Thanks !

• Gus Mueller — Distant Object code
• Jonathan 'Wolf' Rentzsch — JRSwizzle

Questions, comments, patches

Send me a mail !

Patrick Geiller
[email protected]