lib/phantom/modules/detectors.js
function(options) {
    var result = false;
    var el = document.querySelector(options.selector);

    if (el) {
      // el must be an HTMLElement that is visible
      result = el.offsetWidth && el.offsetHeight;
    }

    return result;
  }
function(options) {
    var result = false;
    var el = document.querySelector(options.selector);

    if (el) {
      // el must be an HTMLElement that is visible
      result = el.offsetWidth && el.offsetHeight;
    }

    return result;
  }
Use plain Web API detection, with standard selectors https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Getting_Started/Selectors Returns true on element visibility