IPhone : evaluate Javascript in WebView

I am displaying the webPage in my web view. I want to detect a button is clicked on that page.

code for that button is as follow:

document.getElementById("fileUploadSection").innerHTML = '<button type="button" class="btn btn-primary btn-block findJobsButton" id="txtUploadResume" onclick="validate();ok.performClick();"> </button>';

Problem: How can I detect the button is clicked & my native method is called?

Thanks in advance