NSLog(@"%@", [webView stringByEvaluatingJavaScriptFromString:@"'hello';"]);   // hello
NSLog(@"%@", [webView stringByEvaluatingJavaScriptFromString:@"'hello';'goodbye';"]);   // goodbye
NSLog(@"%@", [webView stringByEvaluatingJavaScriptFromString:@"return 'hello';"]);   //
NSLog(@"%@", [webView stringByEvaluatingJavaScriptFromString:@"var greeting = function(){return 'hello';}; greeting();"]);   //hello

NSLog(@"%@", [webView stringByEvaluatingJavaScriptFromString:@"document.wordOfTheDay = 'discorporate';"]);   //
NSLog(@"%@", [webView stringByEvaluatingJavaScriptFromString:@"document.wordOfTheDay;"]);   //discorporate

if (/loaded|complete/.test(document.readyState))
{
    document.UIWebViewDocumentIsReady = true;
} else
{
    document.addEventListener('DOMContentLoaded', function(){document.UIWebViewDocumentIsReady = true;}, false);
}

-(void)pollDocumentReadyState
{
    if ([@"true" caseInsensitiveCompare:[webview stringByEvaluatingJavaScriptFromString:@"document.UIWebViewDocumentIsReady;"]] == NSOrderedSame)
    {
        NSString *json = [webView stringByEvaluatingJavaScriptFromString:myFancyParsingAndSerializationScript];
	//Do something with json
    } else 
    {
        [self performSelector:@selector(pollDocumentReadyState) withObject:nil afterDelay:1];
    }
}

-(void)beginScrape
{
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(jsEvaluationCompleted:) name:EMKJavascriptEvaluationComplete object:nil];

    NSString *scriptPath = [[NSBundle mainBundle] pathForResource:@"myFancyParsingAndSerializationScript" ofType:@"js"];
    NSString *script = [NSString stringWithContentsOfFile:scriptPath encoding:NSUTF8StringEncoding error:NULL];
    NSURL* url = [NSURL URLWithString: @"http://example.com"];

    EMKJavascriptEvaluation *evaluation = [EMKJavascriptEvaluation evaluateScript:script withHtmlAtURL:url];

    [evaluation injectLibraryAtPath:[[NSBundle mainBundle] pathForResource:@"jquery" ofType:@"js"]];
    [evaluation injectLibraryAtPath:[[NSBundle mainBundle] pathForResource:@"json2" ofType:@"js"]];

    [evaluation evaluate];
}


-(void)jsEvaluationCompleted:(NSNotification*)notification
{
    NSLog(@"result: %@", [[notification object] result]);
}

Background

Arbitrary data and the assumption of prior knowledge

1. Standards based data formats are developed and promoted
2. Browsers directly render common data types (i.e. the most common data formats, which are not necessarily the standards based formats)
3. Browsers provide a plugin mechanism for other data types (the HTML spec provides a mechanism for embedding these plugins in the form of the