fake-intercom-iframe-parent.js

function proxyMethods(proxyObj, originalObj, props) {
  props.forEach(function(method) {
    proxyObj[method] = function() {
      return originalObj[method](...arguments);
    };
  });
}

function proxyProps(proxyObj, originalObj, props) {
  props.forEach(function(prop) {
    Object.defineProperty(proxyObj, prop, {
      get() {
        return originalObj[prop];
      },
      set(val) {
        originalObj[prop] = val;
      }
    });
  });
}

export default function(iframe) {
  const fakeDocument = {};
  const fakeWindow = {document: fakeDocument};

  proxyMethods(fakeDocument, window.document, ['querySelector', 'createElement', 'appendChild', 'getElementById', 'getElementsByTagName', 'addEventListener', 'removeEventListener']);

  proxyMethods(fakeWindow, window, ['addEventListener', 'removeEventListener']);

  proxyProps(fakeDocument, window.document, ['body', 'location']);
  proxyProps(fakeWindow, window, ['Intercom', 'location']);

  iframe.contentWindow.parent = fakeWindow;
}