What the heck is JavaScriptCore? Cesare Rocchi @_funkyboy 

TOC • History • What’s JSCore • Demos • What’s new in WebKit 

Who am I? 

UX designer and developer 

studiomagnolia.com 

upbeat.it 

appversion.io 

podrover.com 

Who are you? 

History 

stringByEvaluatingJavaScriptFromString: 

10.2 

No content

No content

iOS7 

iOS7 

JSContext 

JSValue 

NSString *scriptPath = [[NSBundle mainBundle] pathForResource:@"temperature" ofType:@"js"]; 

NSString *scriptCode = [NSString stringWithContentsOfFile:scriptPath encoding:NSUTF8StringEncoding error:nil]; 

self.context = [[JSContext alloc] init]; [self.context evaluateScript:scriptCode]; 

NSString *scriptPath = [[NSBundle mainBundle] pathForResource:@"temperature" ofType:@"js"]; NSString *scriptCode = [NSString stringWithContentsOfFile:scriptPath encoding:NSUTF8StringEncoding error:nil]; self.context = [[JSContext alloc] init]; [self.context evaluateScript:scriptCode]; 

JS <-> Native 

Blocks 

JSExport 

Demo Objc Demo Swift 

React.js 

#define RCT_EXTERN_REMAP_METHOD(js_name, method) \ - (void)__rct_export__##method { \ __attribute__((used, section("__DATA,RCTExport"))) \ __attribute__((__aligned__(1))) \ static const char *__rct_export_entry__[] = { __func__, #method, #js_name }; \ } https://github.com/facebook/react-native/blob/b99744a164f96be2989d686495a1c7d1afac737a/React/Base/ RCTBridgeModule.h#L141 

Questions? 

No plugins Flash Applets 

The full Safari engine is inside of iPhone. And so, you can write amazing Web 2.0 and Ajax apps that look exactly and behave exactly like apps on the iPhone. SJ, 2007 “ ” 

History • No plugins • Flash • Applets 

No content

Adobe, don’t even think about it! 

No content

No content

History • Nitro was introduced in iOS 4.3 • Uses JIT • Transform JS into native code Needs to mark memory w+x • Security issues 

No content

var temp = {}; temp[10123] = "cocoaconf"; 

Progress 

iOS 3.2 -> iOS4 https://developer.apple.com/LIBRARY/ios/releasenotes/General/iPhone40APIDiffs/index.html Added UIWebView.allowsInlineMediaPlayback Added UIWebView.mediaPlaybackRequiresUserAction 

iOS 4.3 -> iOS5 https://developer.apple.com/LIBRARY/ios/releasenotes/General/iOS50APIDiff/index.html Added UIWebView.mediaPlaybackAllowsAirPlay Added UIWebView.scrollView 

iOS 5.1 -> iOS6 https://developer.apple.com/LIBRARY/ios/releasenotes/General/iOS60APIDiffs/index.html Added UIWebView.keyboardDisplayRequiresUserAction Added UIWebView.suppressesIncrementalRendering 

iOS 6.1 -> iOS7 https://developer.apple.com/library/IOS/releasenotes/General/iOS70APIDiffs/index.html Added UIWebView.gapBetweenPages Added UIWebView.pageCount Added UIWebView.pageLength Added UIWebView.paginationBreakingMode Added UIWebView.paginationMode Added UIWebPaginationBreakingMode Added UIWebPaginationBreakingModeColumn Added UIWebPaginationBreakingModePage Added UIWebPaginationMode Added UIWebPaginationModeBottomToTop Added UIWebPaginationModeLeftToRight Added UIWebPaginationModeRightToLeft Added UIWebPaginationModeTopToBottom Added UIWebPaginationModeUnpaginated 

iOS 6.1 -> iOS7 https://developer.apple.com/library/IOS/releasenotes/General/iOS70APIDiffs/index.html Added #def JSC_OBJC_API_ENABLED Added JSCheckScriptSyntax() Added JSClassRef Added JSContextGroupRef Added JSContextRef Added JSEvaluateScript() Added JSGarbageCollect() Added JSGlobalContextRef Added JSObjectRef Added JSPropertyNameAccumulatorRef Added JSPropertyNameArrayRef Added JSStringRef Added JSValueRef Added #def WTF_EXPORT_PRIVATE Added #def WTF_PLATFORM_IOS Added JSContext Added -[JSContext JSGlobalContextRef] Added +[JSContext contextWithJSGlobalContextRef:] Added +[JSContext currentArguments] Added +[JSContext currentContext] Added +[JSContext currentThis] Added -[JSContext evaluateScript:] Added JSContext.exception Added JSContext.exceptionHandler Added -[JSContext globalObject] Added -[JSContext init] Added -[JSContext initWithVirtualMachine:] Added -[JSContext objectForKeyedSubscript:] Added -[JSContext setObject:forKeyedSubscript:] Added JSContext.virtualMachine Added JSContext(JSContextRefSupport) Added JSContext(SubscriptSupport) Added #def JSContext_h Added JSContextGetGlobalObject() Added JSContextGetGroup() Added JSContextGroupCreate() Added JSContextGroupRelease() Added JSContextGroupRetain() Added JSGlobalContextCreate() Added JSGlobalContextCreateInGroup() Added JSGlobalContextRelease() Added JSGlobalContextRetain() Added JSExport Added #def JSExportAs Added JSManagedValue Added -[JSManagedValue initWithValue:] Added +[JSManagedValue managedValueWithValue:] Added -[JSManagedValue value] Added #def JSManagedValue_h Added JSClassAttributes Added JSClassCreate() Added JSClassDefinition Added JSClassRelease() Added JSClassRetain() Added JSObjectCallAsConstructor() Added JSObjectCallAsConstructorCallback Added JSObjectCallAsFunction() Added JSObjectCallAsFunctionCallback Added JSObjectConvertToTypeCallback Added JSObjectCopyPropertyNames() Added JSObjectDeleteProperty() Added JSObjectDeletePropertyCallback Added JSObjectFinalizeCallback Added JSObjectGetPrivate() Added JSObjectGetProperty() Added JSObjectGetPropertyAtIndex() Added JSObjectGetPropertyCallback Added JSObjectGetPropertyNamesCallback Added JSObjectGetPrototype() Added JSObjectHasInstanceCallback Added JSObjectHasProperty() Added JSObjectHasPropertyCallback Added JSObjectInitializeCallback Added JSObjectIsConstructor() Added JSObjectIsFunction() Added JSObjectMake() Added JSObjectMakeArray() Added JSObjectMakeConstructor() Added JSObjectMakeDate() Added JSObjectMakeError() Added JSObjectMakeFunction() Added JSObjectMakeFunctionWithCallback() Added JSObjectMakeRegExp() Added JSObjectSetPrivate() Added JSObjectSetProperty() Added JSObjectSetPropertyAtIndex() Added JSObjectSetPropertyCallback Added JSObjectSetPrototype() Added JSPropertyAttributes Added JSPropertyNameAccumulatorAddName() Added JSPropertyNameArrayGetCount() Added JSPropertyNameArrayGetNameAtIndex() Added JSPropertyNameArrayRelease() Added JSPropertyNameArrayRetain() Added JSStaticFunction Added JSStaticValue Added kJSClassAttributeNoAutomaticPrototype Added kJSClassAttributeNone Added kJSClassDefinitionEmpty Added kJSPropertyAttributeDontDelete Added kJSPropertyAttributeDontEnum Added kJSPropertyAttributeNone Added kJSPropertyAttributeReadOnly Added JSChar Added JSStringCreateWithCharacters() Added JSStringCreateWithUTF8CString() Added JSStringGetCharactersPtr() Added JSStringGetLength() Added JSStringGetMaximumUTF8CStringSize() Added JSStringGetUTF8CString() Added JSStringIsEqual() Added JSStringIsEqualToUTF8CString() Added JSStringRelease() Added JSStringRetain() Added JSStringCopyCFString() Added JSStringCreateWithCFString() Added JSValue Added -[JSValue JSValueRef] Added -[JSValue callWithArguments:] Added -[JSValue constructWithArguments:] Added JSValue.context Added -[JSValue defineProperty:descriptor:] Added -[JSValue deleteProperty:] Added -[JSValue hasProperty:] Added -[JSValue invokeMethod:withArguments:] Added -[JSValue isBoolean] Added -[JSValue isEqualToObject:] Added -[JSValue isEqualWithTypeCoercionToObject:] Added -[JSValue isInstanceOf:] Added -[JSValue isNull] Added -[JSValue isNumber] Added -[JSValue isObject] Added -[JSValue isString] Added -[JSValue isUndefined] Added -[JSValue objectAtIndexedSubscript:] Added -[JSValue objectForKeyedSubscript:] Added -[JSValue setObject:atIndexedSubscript:] Added -[JSValue setObject:forKeyedSubscript:] Added -[JSValue setValue:atIndex:] Added -[JSValue setValue:forProperty:] Added -[JSValue toArray] Added -[JSValue toBool] Added -[JSValue toDate] Added -[JSValue toDictionary] Added -[JSValue toDouble] Added -[JSValue toInt32] Added -[JSValue toNumber] Added -[JSValue toObject] Added -[JSValue toObjectOfClass:] Added -[JSValue toPoint] Added -[JSValue toRange] Added -[JSValue toRect] Added -[JSValue toSize] Added -[JSValue toString] Added -[JSValue toUInt32] Added -[JSValue valueAtIndex:] Added -[JSValue valueForProperty:] Added +[JSValue valueWithBool:inContext:] Added +[JSValue valueWithDouble:inContext:] Added +[JSValue valueWithInt32:inContext:] Added +[JSValue valueWithJSValueRef:inContext:] Added +[JSValue valueWithNewArrayInContext:] Added +[JSValue valueWithNewErrorFromMessage:inContext:] Added +[JSValue valueWithNewObjectInContext:] Added +[JSValue valueWithNewRegularExpressionFromPattern:flags:inContext:] Added +[JSValue valueWithNullInContext:] Added +[JSValue valueWithObject:inContext:] Added +[JSValue valueWithPoint:inContext:] Added +[JSValue valueWithRange:inContext:] Added +[JSValue valueWithRect:inContext:] Added +[JSValue valueWithSize:inContext:] Added +[JSValue valueWithUInt32:inContext:] Added +[JSValue valueWithUndefinedInContext:] Added JSPropertyDescriptorConfigurableKey Added JSPropertyDescriptorEnumerableKey Added JSPropertyDescriptorGetKey Added JSPropertyDescriptorSetKey Added JSPropertyDescriptorValueKey Added JSPropertyDescriptorWritableKey Added JSValue(JSValueRefSupport) Added JSValue(StructSupport) Added JSValue(SubscriptSupport) Added #def JSValue_h Added JSType Added JSValueCreateJSONString() Added JSValueGetType() Added JSValueIsBoolean() Added JSValueIsEqual() Added JSValueIsInstanceOfConstructor() Added JSValueIsNull() Added JSValueIsNumber() Added JSValueIsObject() Added JSValueIsObjectOfClass() Added JSValueIsStrictEqual() Added JSValueIsString() Added JSValueIsUndefined() Added JSValueMakeBoolean() Added JSValueMakeFromJSONString() Added JSValueMakeNull() Added JSValueMakeNumber() Added JSValueMakeString() Added JSValueMakeUndefined() Added JSValueProtect() Added JSValueToBoolean() Added JSValueToNumber() Added JSValueToObject() Added JSValueToStringCopy() Added JSValueUnprotect() Added kJSTypeBoolean Added kJSTypeNull Added kJSTypeNumber Added kJSTypeObject Added kJSTypeString Added kJSTypeUndefined Added JSVirtualMachine Added -[JSVirtualMachine addManagedReference:withOwner:] Added -[JSVirtualMachine init] Added -[JSVirtualMachine removeManagedReference:withOwner:] Added #def AVAILABLE_AFTER_WEBKIT_VERSION_5_1 Added #def AVAILABLE_WEBKIT_VERSION_1_3_AND_LATER_BUT_DEPRECATED_AFTER_WEBKIT_VERSION_5_1 Added #def WEBKIT_OBJC_METHOD_ANNOTATION Added #def WEBKIT_VERSION_1_0 Added #def WEBKIT_VERSION_1_1 Added #def WEBKIT_VERSION_1_2 Added #def WEBKIT_VERSION_1_3 Added #def WEBKIT_VERSION_2_0 Added #def WEBKIT_VERSION_3_0 Added #def WEBKIT_VERSION_3_1 Added #def WEBKIT_VERSION_4_0 Added #def WEBKIT_VERSION_LATEST Added #def WEBKIT_VERSION_MAX_ALLOWED Added #def WEBKIT_VERSION_MIN_REQUIRED 232 APIs } 

No content

iOS7 -> iOS8 https://developer.apple.com/library/prerelease/ios/releasenotes/General/iOS80APIDiffs/frameworks/WebKit.html 

1 Class 1 Protocol 

UIWebView UIWebViewDelegate 

14 Classes 3 Protocols 

WKWebView WKFrameInfo WKBackForwardList WKBackForwardListItem WKNavigation WKNavigationAction WKNavigationResponse WKPreferences WKProcessPool WKUserContentController WKWebViewConfiguration WKWindowFeatures WKScriptMessage WKUserScript WKNavigationDelegate WKScriptMessageHandler WKUIDelegate 

XPC • Greatly improved in iOS8 • Third party keyboards • Sharing extensions 

XPC find /Applications -name \*.xpc | grep Web | wc -l 

XPC • Split app in multiple processes • E.g. Sourcekit • http://www.jpsim.com/uncovering-sourcekit/ 

r167958 

No content

Optimizing JS 

Wat? https://www.youtube.com/watch?v=20BySC_6HyY 

jsc sudo ln -s /System/Library/Frameworks/ JavaScriptCore.framework/Versions/Current/Resources/jsc /bin/jsc 

JS bytecode LLInt JIT DFG optimization 

function sum(a, b) { return a + b; } 

LLInt JIT DFG optimization function sum(a, b) { return a + b; } 

LLInt JIT DFG 

LLVM 

LLVM • Infrastructure • Meant to optimize *time • Started by Mr. Swift 

LLInt JIT DFG 

LLInt JIT DFG FTL 

What’s new 

Observable values 

Observable values • loading • title • URL • estimatedProgress 

Observable values webView.addObserver(self, forKeyPath: "loading", options: .New, context: nil) 

Observable values override func observeValueForKeyPath(...) { switch keyPath { case "loading": println("\(webView.loading)") case "estimatedProgress": println("\(webView.estimatedProgress)") … } } 

Injecting 

Action Request Response Rendering 

Action Request Response Rendering 

Action Request 

Action Request webView:decidePolicyForNavigationAction:decisionHandler 

Response Rendering 

Response Rendering webView:decidePolicyForNavigationResponse:decisionHandler: 

func webView(webView: WKWebView!, decidePolicyForNavigationAction navigationAction: WKNavigationAction!, decisionHandler: ((WKNavigationActionPolicy) -> Void)!) { if (navigationAction.navigationType == .LinkActivated && navigationAction.request.URL.host?. lowercaseString.hasPrefix("cocoaconference.com/") != nil) { // Open Safari UIApplication.sharedApplication().openURL(navigationAction.request.URL); decisionHandler(.Cancel) } else { decisionHandler(.Allow) } } 

Native code HTML Page JS Data 

Data is serialized into native objects! 

Injecting 1. Create configuration 2. Wrap JS script in a WKUserScript 3. Add script to configuration controller 4. Set up handler 5. Use configuration to build a Web view 

let speakersWebViewConfiguration = WKWebViewConfiguration() 

let scriptURL = NSBundle.mainBundle().pathForResource("fetchSpeakers", ofType: “js") let jsScript = String(contentsOfFile:scriptURL, encoding:NSUTF8StringEncoding, error: nil) let fetchAuthorsScript = WKUserScript(source: jsScript, injectionTime: .AtDocumentEnd, forMainFrameOnly: true) 

speakersWebViewConfiguration. userContentController. addUserScript(fetchAuthorsScript) 

speakersWebViewConfiguration. userContentController. addScriptMessageHandler(self, name: MESSAGE_HANDLER) 

speakersWebView = WKWebView(frame: CGRectZero, configuration: speakersWebViewConfiguration) 

speakersWebView.addObserver(self, forKeyPath: "loading", options: .New, context: nil) speakersWebView.addObserver(self, forKeyPath: "estimatedProgress", options: .New, context: nil) 

let speakersRequest = NSURLRequest(URL:speakersURL) speakersWebView!.loadRequest(speakersRequest) 

No content

No content

No content

No content

No content

Demo 

https://github.com/ funkyboy/Cocoaconf- SanJose-2015 

Caution 

https://developer.apple.com/app-store/review/guidelines/ 

https://developer.apple.com/app-store/review/guidelines/ 

https://developer.apple.com/app-store/review/guidelines/ 

https://developer.apple.com/app-store/review/guidelines/ 

https://developer.apple.com/programs/terms/ios/standard/ ios_program_standard_agreement_20140909.pdf An Application may not download or install executable code. Interpreted code may only be used in an Application if all scripts, code and interpreters are packaged in the Application and not downloaded. The only exception to the foregoing is scripts and code downloaded and run by Apple's built- in WebKit framework, provided that such scripts and code do not change the primary purpose of the Application by providing features or functionality that are inconsistent with the intended and advertised purpose of the Application as submitted to the App Store. 

https://developer.apple.com/programs/terms/ios/standard/ ios_program_standard_agreement_20140909.pdf An Application may not download or install executable code. Interpreted code may only be used in an Application if all scripts, code and interpreters are packaged in the Application and not downloaded. The only exception to the foregoing is scripts and code downloaded and run by Apple's built- in WebKit framework, provided that such scripts and code do not change the primary purpose of the Application by providing features or functionality that are inconsistent with the intended and advertised purpose of the Application as submitted to the App Store. 

Building a native app is like building a custom browser 

Building a native app is like building a custom browser Me, now 

Summing up 

No content

Links • https://www.webkit.org/blog/3362/ introducing-the-webkit-ftl-jit/ • http://trac.webkit.org/changeset/167958 • https://www.destroyallsoftware.com/ talks/wat • WWDC Video #206 

Contact • [email protected] • @_funkyboy