This document discusses using JavaScriptCore to extend the functionality of apps. It provides an example of using JavaScriptCore to evaluate JavaScript code and access the results. It also outlines how JavaScriptCore maps JavaScript types to Objective-C and Swift types. The document describes how JavaScriptCore creates a virtual machine and handles single-threaded execution. It then shows how to export Swift classes to JavaScript using a protocol. Finally, it lists some ways apps like Paw could leverage JavaScriptCore, such as for code generators, importers, and dynamic values.

1. Extend Your App With
JavaScriptCore
Micha MAZAHERI
iOS > Mac > Python > React
@mittsh

5. API Blueprint
Integration?

6. How can we make
Paw hackable with
JavaScriptCore?

7. Open
Source
Clean Your App
FocusSmall
Apps

8. Updates

9. Updates

11. CocoaScript

13. WebKit

14. Your JS API
Interface
Contract
Testing Use it
Like it?

15. Example
JSContext* context = [[JSContext alloc] init];
JSValue* gigaValue = [context evaluateScript:@"Math.pow(2,30)"];
NSLog(@"1 GiB = %ld bytes", [gigaValue toNumber].integerValue);
// 1 GiB = 1073741824 bytes

16. JSValue
JavaScript Type Objective-C Type Swift Type
string NSString String
boolean BOOL Bool
number
NSNumber
double
int32_t
uint32_t
NSNumber!
Double
Int32
UInt32
Date NSDate Date
Array NSArray [AnyObject]
Object NSDictionary [NSObject : AnyObject]
Object custom type custom type

17. JSContext
Virtual
Machine
Holds All
Objects
Single
Thread

18. JSExport
Swift
Class
JavaScript
Prototype
Swift
Instance
JavaScript
Object

19. /* Extend JSExport protocol */
@protocol LMJSRequest <JSExport>
JSExportAs(getMethod, -(id)method);
JSExportAs(getUrl, -(id)url);
JSExportAs(setMethod, -(id)method:(NSString*)method);
JSExportAs(setUrl, -(id)url:(NSString*)url);
@end
/* Implement protocol as a category */
@interface LMRequest (LMJSRequest) <LMJSRequest>
@end

20. Not The Web
DOM WebWorkers Web Crypto
Local Storage
XHR (Ajax)setTimeout
CSS
PromiseWebSocket
File API

21. Not The Web
Pure Vanilla JS

22. Multithreading
Core Data Grand
Central
Dispatch

23. Run Loop
setTimeout()
DispatchQueue.main.asyncAfter(deadline: time)
…run code…

24. Extensions in Paw
ImportersCode
Generators
Dynamic
Values

25. Code Generators
• Client Code (Swift, ObjC, Python, Ruby…)
• Command Line (cURL, HTTPie)
• API Descriptions (API Blueprint, Swagger, RAML…)
• 3rd party (Postman)

26. Importers
• HTTP Archives (HAR)
• API Descriptions (API Blueprint, Swagger, RAML…)
• 3rd party (Postman)

27. Dynamic Values
• Auth (JWT, Digest, Django…)
• 3rd party auth (Amazon, Auth0…)
• Randomizers (Chance.js, UUID, JSON Schema)

28. Who uses JavaScriptCore?
React NativeSafari Build Apps

29. Conclusion
• We can open source more
• Always have an answer
• More features than any competitor
• Update extensions multiple times a week

30. Thank You
https://paw.cloud
@mittsh