Question

I have an html file that has a <div> and that I am loading into a UIWebView and I need to know how many lines of text are in the div, so I can check that with javascript:

<script>
function countLines() {
    var divHeight = document.getElementById('myDiv').offsetHeight;
    var lineHeight = parseInt(document.getElementById('myDiv').style.lineHeight);
    var lines = divHeight / lineHeight;
    alert("Lines: " + lines);
}
</script>

and it does alert the variable “lines”

In Objective-C how can I retrieve this variable from my UIWebView and then use it in my code?

Thankyou!

Answer 1

The UIWebView method stringByEvaluatingJavaScriptFromString: is the sole interface to the JavaScript environment. It evaluates and returns a string representation of the value of a JavaScript expression you pass to it. So, for example:

// simplified expression, no function needed
NSString *expr = @"document.getElementById('myDiv').offsetHeight / document.getElementById('myDiv').style.lineHeight";
// now pass it to the web view and parse the result
int lines = [[self.webView stringByEvaluatingJavaScriptFromString:expr] intValue];