9 ms·

Apple’s iOS7 Native JavaScript Bridge

116 points by bananacurve 13y ago

cwp 13y ago
I wonder if Apple would approve an app that downloads and executes Javascript using the bridge. Historically, Javascript has been an exception to the blanket rule against downloading code, but outside of a web view, that might not hold.
- interpol_p 13y ago
  Interestingly, a few apps seem to download code and run it. GamePress, a drag-and-drop game editor does this. Featuring an "Arcade" where you can download others' games. And Editorial, a Python-based writing tool allows one to download and execute "workflows," which include Python scripts. We were asked by Apple to remove code sharing features from our own app. I am hoping that they are no longer enforcing this policy.
nilliams 13y ago
There was a great talk on this at Cascadia JS, 'JavaScript as a first-class citizen on iOS7': https://www.youtube.com/watch?v=y-nodF6Cp1Y https://www.youtube.com/watch?v=y-nodF6Cp1Y
- tehwebguy 13y ago
  Just watched the entire thing, very cool. Near the end he sets up a scene, physics and tap events to create new objects on the screen with a few lines of JavaScript. All of the heavy lifting is handled natively in iOS SpriteKit and it runs at 60 fps.
  - nilliams 13y ago
    Yes I meant to come back to this comment and explain why people should watch it. What you said!
  - phoboslab 13y ago
    You might be interested in Ejecta[1] then. X-Type[2], a game I made with it, easily draw hundreds of sprites with 60fps. [1] http://impactjs.com/ejecta http://impactjs.com/ejecta [2] https://itunes.apple.com/us/app/x-type/id597488149?mt=8 https://itunes.apple.com/us/app/x-type/id597488149?mt=8
pflats 13y ago
"Apple’s iOS7 support of JavaScript inline with your Objective-C code validates JavaScript as the leading (and only) non proprietary language that is supported within the iOS development environment by the device manufacturer." Since when is Objective-C proprietary? Apple's given it a few non-standard extensions (i.e. blocks) but that doesn't make it a proprietary language. GCC and Clang are open source.
- bananacurve 13y ago
  Technically true, but Cocoa is proprietary. Is ObjC widely used for anything else?
  - mmariani 13y ago
    Cocotron [1] is another alternative that can target Windows and even Linux with some exceptions. [1] http://www.cocotron.org http://www.cocotron.org
  - eonil 13y ago
    Check out Apportable. And proprietary doesn't mean narrowly used. Also open doesn't mean widely used. Bringing Cocoa was a good trial, but doesn't make the text correct.
    - bananacurve 13y ago
      No it does not make the text correct, people often conflate ObjC and Cocoa. Thanks for mentioning Apportable.
    - lambda 13y ago
      Well, when people talk about ObjC development on Mac and iOS platforms, they generally mean ObjC plus Cocoa or Cocoa Touch. It's true that ObjC itself isn't what's proprietary, but Cocoa and Cocoa Touch are.
      - randomdata 13y ago
georgemcfly 13y ago
Objective-C isn't a proprietary language, as this author annoyingly suggests several times. Regardless, the new JavaScriptCore framework is pretty impressive. It would be nice if there were some official Apple docs beyond the one WWDC video, though.
- mattschmulen 13y ago
  I agree, it was a bit tough to find good docs and references. If anyone has other good references I would love to check it out.
  - lazerwalker 13y ago
    It might not be that helpful, but you can actually download the JavaScriptCore source directly from the WebKit trunk (http://svn.webkit.org/repository/webkit/trunk/Source/JavaScriptCore/ http://svn.webkit.org/repository/webkit/trunk/Source/JavaScr...). It's worth noting that there are some discrepancies between that codebase and the actual behavior of the public iOS 7 framework, but if you're not doing anything too crazy it probably won't be an issue.
eonil 13y ago
JSC was always there for years in WebKit source repository, and anybody could build native JSC engine. Well, it needs some extra works, but there're also some Github repos from other people. AFAIK, the only difference to Safari was JIT compilation support. Because iOS doesn't allow executing dynamically generated machine code in 3rd-party apps for security reason. Does iOS7 support JIT compilation on JSC embedded in any app? If it supports JIT, that could be a big news, because it means Apple finally allowed dynamically generated code in 3rd-party apps, but I don't think the day will come. And personally, I don't see any benefit from JavaScript apps. If someone claims JS or any third party frameworks are better than Objective-C for iOS app, I would like to ask these things. (could be offensive, but these are actually how I feel from those claims) Does it offer better auto-completion? Does it offer better syntax/semantic/type checks? Does it offer better debugging aid? (like GDB's execution rollback) Does it offer better accessibility to any platform features? Can I use new features immediately? Shouldn't I wait for 3rd party patch? Profiler for device and simulators? How's low-level access? If I have some trouble, how can I fix it without knowledge for lower-level (Cocoa/Darwin)? If I want to use C-based DSL? Is it safe for AppStore approval? What's the benefit of using open language on proprietary platform? I mean, what's better with JS than Objective-C with Xcode? If it can't offer any of those stuffs, it means it's at least 10 times less productive = 10 times more cost. Well, it could make sense JS app for an Android app because ADT is too sucks so some extra wrapper can bring extra productivity. But for iOS, JS stuffs only degrade productivity by extra abstraction, debugging hardness and inferior toolsets.
- apaprocki 13y ago
  AFAIK they will never allow JIT. It isn't so much banning JIT as it is the kernel providing no way for applications to mark memory pages executable. Marking memory executable is how JIT compilers function, but it also prevents other uses.
  - phoboslab 13y ago
    I still have hopes that Apple cares enough and finds a way to whitelist the JSC lib somehow. Not sure exactly how that would work, because permissions to allocate executable memory is given per process on iOS. But I guess they could inspect the call stack to see if the allocating call indeed comes from the built-in JSC lib?
general_failure 13y ago
Appcelerator cannot use v8 because v8 has no non-jit mode. Ios apps cannot jit...
- phoboslab 13y ago
  Whitelisted Apps can. Mobile Safari for instance uses the JavaScriptCore JIT; Chrome however does not, despite using Apple's built-in WebView.
  - CodeWithCoffee 13y ago
    I would be interested to know how that whitelist is implemented. I would suspect that the default apps (Safari, Mail, iTunes, etc) are compiled to use a custom implementation of UIWebView that uses JIT (which would completely prevent Chrome from using JIT), but it would be interesting if there is a switch (perhaps by a plist key) that Apple could flip, so a few selected apps could get access without the need to do compile against private libraries.
    - bdash 13y ago
      An entitlement.
martin_ 13y ago
Sounds very similar to http://www.cycript.org/ http://www.cycript.org/
comex 13y ago
Incidentally, on my retina MBP in Safari, the entire text of this post somehow manages to appear scaled up and blurry. Doesn't happen in Chrome.
stevejohnson 13y ago
Does anyone have benchmarks about JIT vs non-JIT Javascript on iOS 7? I'm interested, but haven't been able to locate any.
- eonil 13y ago
  This is not JSC, and just using UIWebView, but would be good enough to estimate approximated difference. http://iao.fi/myposts/uiwebview http://iao.fi/myposts/uiwebview The author is claiming the difference would be about 5x. I think that's reasonable.
pdenya 13y ago
That syntax for passing obj-c blocks to javascript is nice. I've never been a fan of titanium/phonegap but this might make it easy and fast enough to be worthwhile. Ideally I could use html for some complex interfaces seamlessly and keep native components (scrollviews, etc) elsewhere.
sjtgraham 13y ago
I've been working with JavaScriptCore to facilitate the optional code-on demand constraint of REST, e.g. A client requests a JS representation of a resource, which includes what fields a valid resource has, type hinting so the client can dynamically build a UITableView with the most appropriate controls for each field, and validation functions allowing the client to validate a field when it changes or when its UITextField resigns first responder status. I just had a horrifying thought: Aren't apps that download code banned from the App Store? If so, would this include JS downloaded at runtime to be evaluated with JavaScriptCore? What's the conceptual difference between this and a UIWebView opening a page that has <script> tags embedded?
- cpleppert 13y ago
  3.3.2 An Internal Use 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. I take this to mean that the javascript has to be downloaded by the webkit/uiwebview as part of an web page and you can't supply the javascript externally if you get if off the network.. There is a lot of confusion online on this point(some people disagree) but that is my understanding.
  - sjtgraham 13y ago
    Thanks, JSC is part of Webkit so I hope it is allowed. I've emailed John Geleynse (the contact listed at the end of the WWDC talk) to get a concrete answer from Apple. It would be such a terrible waste if they disallow this. It looks like there is a way to get the JavaScriptContext of a UIWebView using KVC, but it's not clear if that is "undocumented" and therefore private, because the whole framework is basically undocumented.
riq_ 13y ago
Shameless plug here: In case you need to use JS on older iOS versions, I created JavaScript bridge for Objective-C (and C). It is a command line tool that parses Objective-C header files (using llvm) and generates the needed intermediate "bridge" files. Internally it uses the SpiderMonkey VM (instead of JavaScript Core) The source code and the documentation can be found here: https://github.com/ricardoquesada/jsbindings https://github.com/ricardoquesada/jsbindings
tylerlarson 13y ago
The iPad app that I've been working on was partially built with Ejecta, which uses the JavaScriptCore to eval JavaScript and pairs this with OpenGL ES to implement the Canvas and WebGL APIs. You can see it here if interested https://itunes.apple.com/us/app/paperless-post-invitations/id489940389?mt=8 https://itunes.apple.com/us/app/paperless-post-invitations/i...
United857 13y ago
Very cool -- but would be nice if they could tie this into the DOM and JS context of a UIWebView, so we could have true HTML5/hybrid native apps.
Zelphyr 13y ago
I recognize this is pedantic but why does he keep using "surface" as a verb? Is there some new programming nomenclature I'm just now getting exposed to? If so, what does this mean? It reminds me of a Java programmer I used to work with who constantly said he was "hydrating" his objects. I kept wanting to tell him he wasn't sounding as cool as he thought he was.
- alexandros 13y ago
  Surface is a legitimate verb, just like any other. Perhaps the author isn't native, and is using a different verb than the one you'd like. Or perhaps that's how he feels like expressing himself. But it is shocking you'd think this is a worthwhile comment and others would upvote you on it. It's quite sad that this comment is currently the top comment, in an article that raises quite an important topic for the JS and iOS developer communities. As much as I loathe the "hn is turning into reddit" crowd, this is much worse. HN is turning into a criticism machine that when it can't find anything worthwhile to criticise, will literally criticise anything at all rather than elevate a positive comment to the top.
  - pflats 13y ago
    On the second half of your post: I feel like this happens when people find the basic idea of the article (JS is now a first-class language on iOS!) interesting enough to upvote, but the article itself isn't anything exciting beyond that. The top comments are people's reaction to the articles. Right now, they're "the article keeps calling Obj-C proprietary, but it's totes not"; "that's cool and all, and here's some history, but how is this better than Obj-C"; and "here's a talk about it on youtube". If there's more interesting conversation to be had, someone would have submitted it. You could have submitted it! I read through every other top-level comment, and didn't find any of them were particularly interesting. Is there some conversation that you think is worth having? (But yeah, surface is a totally legit verb, makes sense in this context (bringing an Obj-C object into JS), and it was only used twice anyway.)
    - Zelphyr 13y ago
AsymetricCom 13y ago
If you're reading this and picking up new information (besides strongloop's Titanium pitch) you're really in the dark about what's going on.

116 points by bananacurve 13y ago

cwp 13y ago

I wonder if Apple would approve an app that downloads and executes Javascript using the bridge. Historically, Javascript has been an exception to the blanket rule against downloading code, but outside of a web view, that might not hold.

interpol_p 13y ago
Interestingly, a few apps seem to download code and run it. GamePress, a drag-and-drop game editor does this. Featuring an "Arcade" where you can download others' games. And Editorial, a Python-based writing tool allows one to download and execute "workflows," which include Python scripts. We were asked by Apple to remove code sharing features from our own app. I am hoping that they are no longer enforcing this policy.

nilliams 13y ago

There was a great talk on this at Cascadia JS, 'JavaScript as a first-class citizen on iOS7': https://www.youtube.com/watch?v=y-nodF6Cp1Y https://www.youtube.com/watch?v=y-nodF6Cp1Y

tehwebguy 13y ago
Just watched the entire thing, very cool. Near the end he sets up a scene, physics and tap events to create new objects on the screen with a few lines of JavaScript. All of the heavy lifting is handled natively in iOS SpriteKit and it runs at 60 fps.
- nilliams 13y ago
  Yes I meant to come back to this comment and explain why people should watch it. What you said!
- phoboslab 13y ago
  You might be interested in Ejecta[1] then. X-Type[2], a game I made with it, easily draw hundreds of sprites with 60fps. [1] http://impactjs.com/ejecta http://impactjs.com/ejecta [2] https://itunes.apple.com/us/app/x-type/id597488149?mt=8 https://itunes.apple.com/us/app/x-type/id597488149?mt=8

pflats 13y ago

"Apple’s iOS7 support of JavaScript inline with your Objective-C code validates JavaScript as the leading (and only) non proprietary language that is supported within the iOS development environment by the device manufacturer." Since when is Objective-C proprietary? Apple's given it a few non-standard extensions (i.e. blocks) but that doesn't make it a proprietary language. GCC and Clang are open source.

bananacurve 13y ago
Technically true, but Cocoa is proprietary. Is ObjC widely used for anything else?
- mmariani 13y ago
  Cocotron [1] is another alternative that can target Windows and even Linux with some exceptions. [1] http://www.cocotron.org http://www.cocotron.org
- eonil 13y ago
  Check out Apportable. And proprietary doesn't mean narrowly used. Also open doesn't mean widely used. Bringing Cocoa was a good trial, but doesn't make the text correct.
  - bananacurve 13y ago
    No it does not make the text correct, people often conflate ObjC and Cocoa. Thanks for mentioning Apportable.
  - lambda 13y ago
    Well, when people talk about ObjC development on Mac and iOS platforms, they generally mean ObjC plus Cocoa or Cocoa Touch. It's true that ObjC itself isn't what's proprietary, but Cocoa and Cocoa Touch are.
    - randomdata 13y ago

georgemcfly 13y ago

Objective-C isn't a proprietary language, as this author annoyingly suggests several times. Regardless, the new JavaScriptCore framework is pretty impressive. It would be nice if there were some official Apple docs beyond the one WWDC video, though.

mattschmulen 13y ago
I agree, it was a bit tough to find good docs and references. If anyone has other good references I would love to check it out.
- lazerwalker 13y ago
  It might not be that helpful, but you can actually download the JavaScriptCore source directly from the WebKit trunk (http://svn.webkit.org/repository/webkit/trunk/Source/JavaScriptCore/ http://svn.webkit.org/repository/webkit/trunk/Source/JavaScr...). It's worth noting that there are some discrepancies between that codebase and the actual behavior of the public iOS 7 framework, but if you're not doing anything too crazy it probably won't be an issue.

eonil 13y ago

JSC was always there for years in WebKit source repository, and anybody could build native JSC engine. Well, it needs some extra works, but there're also some Github repos from other people. AFAIK, the only difference to Safari was JIT compilation support. Because iOS doesn't allow executing dynamically generated machine code in 3rd-party apps for security reason. Does iOS7 support JIT compilation on JSC embedded in any app? If it supports JIT, that could be a big news, because it means Apple finally allowed dynamically generated code in 3rd-party apps, but I don't think the day will come. And personally, I don't see any benefit from JavaScript apps. If someone claims JS or any third party frameworks are better than Objective-C for iOS app, I would like to ask these things. (could be offensive, but these are actually how I feel from those claims) Does it offer better auto-completion? Does it offer better syntax/semantic/type checks? Does it offer better debugging aid? (like GDB's execution rollback) Does it offer better accessibility to any platform features? Can I use new features immediately? Shouldn't I wait for 3rd party patch? Profiler for device and simulators? How's low-level access? If I have some trouble, how can I fix it without knowledge for lower-level (Cocoa/Darwin)? If I want to use C-based DSL? Is it safe for AppStore approval? What's the benefit of using open language on proprietary platform? I mean, what's better with JS than Objective-C with Xcode? If it can't offer any of those stuffs, it means it's at least 10 times less productive = 10 times more cost. Well, it could make sense JS app for an Android app because ADT is too sucks so some extra wrapper can bring extra productivity. But for iOS, JS stuffs only degrade productivity by extra abstraction, debugging hardness and inferior toolsets.

apaprocki 13y ago
AFAIK they will never allow JIT. It isn't so much banning JIT as it is the kernel providing no way for applications to mark memory pages executable. Marking memory executable is how JIT compilers function, but it also prevents other uses.
- phoboslab 13y ago
  I still have hopes that Apple cares enough and finds a way to whitelist the JSC lib somehow. Not sure exactly how that would work, because permissions to allocate executable memory is given per process on iOS. But I guess they could inspect the call stack to see if the allocating call indeed comes from the built-in JSC lib?

general_failure 13y ago

Appcelerator cannot use v8 because v8 has no non-jit mode. Ios apps cannot jit...

phoboslab 13y ago
Whitelisted Apps can. Mobile Safari for instance uses the JavaScriptCore JIT; Chrome however does not, despite using Apple's built-in WebView.
- CodeWithCoffee 13y ago
  I would be interested to know how that whitelist is implemented. I would suspect that the default apps (Safari, Mail, iTunes, etc) are compiled to use a custom implementation of UIWebView that uses JIT (which would completely prevent Chrome from using JIT), but it would be interesting if there is a switch (perhaps by a plist key) that Apple could flip, so a few selected apps could get access without the need to do compile against private libraries.
  - bdash 13y ago
    An entitlement.

martin_ 13y ago

Sounds very similar to http://www.cycript.org/ http://www.cycript.org/

comex 13y ago

Incidentally, on my retina MBP in Safari, the entire text of this post somehow manages to appear scaled up and blurry. Doesn't happen in Chrome.

stevejohnson 13y ago

Does anyone have benchmarks about JIT vs non-JIT Javascript on iOS 7? I'm interested, but haven't been able to locate any.

eonil 13y ago
This is not JSC, and just using UIWebView, but would be good enough to estimate approximated difference. http://iao.fi/myposts/uiwebview http://iao.fi/myposts/uiwebview The author is claiming the difference would be about 5x. I think that's reasonable.

pdenya 13y ago

That syntax for passing obj-c blocks to javascript is nice. I've never been a fan of titanium/phonegap but this might make it easy and fast enough to be worthwhile. Ideally I could use html for some complex interfaces seamlessly and keep native components (scrollviews, etc) elsewhere.

sjtgraham 13y ago

I've been working with JavaScriptCore to facilitate the optional code-on demand constraint of REST, e.g. A client requests a JS representation of a resource, which includes what fields a valid resource has, type hinting so the client can dynamically build a UITableView with the most appropriate controls for each field, and validation functions allowing the client to validate a field when it changes or when its UITextField resigns first responder status. I just had a horrifying thought: Aren't apps that download code banned from the App Store? If so, would this include JS downloaded at runtime to be evaluated with JavaScriptCore? What's the conceptual difference between this and a UIWebView opening a page that has <script> tags embedded?

cpleppert 13y ago
3.3.2 An Internal Use 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. I take this to mean that the javascript has to be downloaded by the webkit/uiwebview as part of an web page and you can't supply the javascript externally if you get if off the network.. There is a lot of confusion online on this point(some people disagree) but that is my understanding.
- sjtgraham 13y ago
  Thanks, JSC is part of Webkit so I hope it is allowed. I've emailed John Geleynse (the contact listed at the end of the WWDC talk) to get a concrete answer from Apple. It would be such a terrible waste if they disallow this. It looks like there is a way to get the JavaScriptContext of a UIWebView using KVC, but it's not clear if that is "undocumented" and therefore private, because the whole framework is basically undocumented.

riq_ 13y ago

Shameless plug here: In case you need to use JS on older iOS versions, I created JavaScript bridge for Objective-C (and C). It is a command line tool that parses Objective-C header files (using llvm) and generates the needed intermediate "bridge" files. Internally it uses the SpiderMonkey VM (instead of JavaScript Core) The source code and the documentation can be found here: https://github.com/ricardoquesada/jsbindings https://github.com/ricardoquesada/jsbindings

tylerlarson 13y ago

The iPad app that I've been working on was partially built with Ejecta, which uses the JavaScriptCore to eval JavaScript and pairs this with OpenGL ES to implement the Canvas and WebGL APIs. You can see it here if interested https://itunes.apple.com/us/app/paperless-post-invitations/id489940389?mt=8 https://itunes.apple.com/us/app/paperless-post-invitations/i...

United857 13y ago

Very cool -- but would be nice if they could tie this into the DOM and JS context of a UIWebView, so we could have true HTML5/hybrid native apps.

Zelphyr 13y ago

I recognize this is pedantic but why does he keep using "surface" as a verb? Is there some new programming nomenclature I'm just now getting exposed to? If so, what does this mean? It reminds me of a Java programmer I used to work with who constantly said he was "hydrating" his objects. I kept wanting to tell him he wasn't sounding as cool as he thought he was.

alexandros 13y ago
Surface is a legitimate verb, just like any other. Perhaps the author isn't native, and is using a different verb than the one you'd like. Or perhaps that's how he feels like expressing himself. But it is shocking you'd think this is a worthwhile comment and others would upvote you on it. It's quite sad that this comment is currently the top comment, in an article that raises quite an important topic for the JS and iOS developer communities. As much as I loathe the "hn is turning into reddit" crowd, this is much worse. HN is turning into a criticism machine that when it can't find anything worthwhile to criticise, will literally criticise anything at all rather than elevate a positive comment to the top.
- pflats 13y ago
  On the second half of your post: I feel like this happens when people find the basic idea of the article (JS is now a first-class language on iOS!) interesting enough to upvote, but the article itself isn't anything exciting beyond that. The top comments are people's reaction to the articles. Right now, they're "the article keeps calling Obj-C proprietary, but it's totes not"; "that's cool and all, and here's some history, but how is this better than Obj-C"; and "here's a talk about it on youtube". If there's more interesting conversation to be had, someone would have submitted it. You could have submitted it! I read through every other top-level comment, and didn't find any of them were particularly interesting. Is there some conversation that you think is worth having? (But yeah, surface is a totally legit verb, makes sense in this context (bringing an Obj-C object into JS), and it was only used twice anyway.)
  - Zelphyr 13y ago

AsymetricCom 13y ago

If you're reading this and picking up new information (besides strongloop's Titanium pitch) you're really in the dark about what's going on.