fb.js

function findElement(options, instances) {
  var React = require("React");
  var ReactMount = require("ReactMount");
  var ret = null;
  
  if (!instances) instances = ReactMount._instancesByReactRootID;

  for (n in instances) {
    var instance = instances[n];

    if (!instance) continue;
    var element = instance._currentElement;

    if (options.name) {
      if (element && element.type && element.type.displayName == options.name) {
        return instance.getPublicInstance().getDOMNode();
      }
    } else if (options.id) {
      if (instance._rootNodeID == options.id) {
        if (element.type.displayName) {
          console.log(element.type.displayName);
        } else {
          console.log(element.type);
        }
        return instance;
      }
    }
    if (typeof instance._stringText === 'string') continue;

    if (instance._renderedComponent) {
      ret = findElement(options, { a: instance._renderedComponent });
    }

    var children = instance._renderedChildren;
    if (!ret && children) {
      ret = findElement(options, children);
    }

    if (ret) return ret;
  }

  return null;
}

var a = findElement({ name: "MessengerSettingsMenu" });
var b = findElement({ id: ".0.1.$0.0.0.$1" });