uiwebview javascript no return

Question

have a weird behaviour. In a UIWebView I have a javacript function to detect the postion of an element. this one:

function getPosition(element){

    var el = element;
    var pos = [el.offsetLeft, el.offsetTop];
    var parent = el.offsetParent;
    if (parent != el) {
        while (parent) {
            pos[0] += parent.offsetLeft;
            pos[1] += parent.offsetTop;
            parent = parent.offsetParent;
        }
    }
    //alert(pos);
    return pos;
}

nothing special… but when I call the function like that:

NSString *position = [browserWebView stringByEvaluatingJavaScriptFromString:@"getPosition(document.getElementById('exampleElement'));"];

I get an empty NSString back. When I insert an alert into the function (which is uncomment right now) I get the correct position in the alert!!

Why do I not get the value back and getting just an empty string when the correct return value pos seems to be there?

carlossless · Accepted Answer · 2012-09-27 18:56:57Z

3

This is rather simple and a complete mystery to me at the same time. I don't know why but "stringByEvaluatingJavaScriptFromString:" likes for the javascript result to already resemble a string. To fix your code just add a join() function to your returning array:

return pos.join();

This will join the array into a single string and it will pass as an NSString no problem.

I presume the reason alerts work is that it wouldn't break sites that display data in a similar manner.

answered Sep 27, 2012 at 18:56

carlossless

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carlossless Over a year ago

No problem, if my answer works, you might want to accept it. That's how stackoverflow works. Read: How does accepting an answer work?

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