Question

I am trying to return a string from Javascript:

   [myWebView stringByEvaluatingJavaScriptFromString:@"myJavaScriptFunction()"];

for short strings, the return is OK.
However, when I return a very long string(say 5000 characters in the string), I couldn’t get anything.

So I am guessing it might due to the NSString Size limitation OR my “var jvString” size limitation.

Please help. Thanks

Answer 1

When the method stringByEvaluatingJavaScriptFromString returns nil, it means something has gone wrong. This is most likely not because of NSString size limitations, but for one of the following reasons:

• the javascript execution took longer than 10 seconds
• the script allocated more than 10 MB

From the documentation:

JavaScript execution time is limited to 10 seconds for each top-level
entry point. If your script executes for more than 10 seconds, the web
view stops executing the script. This is likely to occur at a random
place in your code, so unintended consequences may result. This limit
is imposed because JavaScript execution may cause the main thread to
block, so when scripts are running, the user is not able to interact
with the webpage.

JavaScript allocations are also limited to 10 MB. The web view raises
an exception if you exceed this limit on the total memory allocation
for JavaScript.