# Build dev failed: Cannot read property 'indexOf' of undefined **URL:** \ **Category:** ionic-v3\ **Created:** [November 28, 2016, 1:47am UTC](https://forum.ionicframework.com/t/build-dev-failed-cannot-read-property-indexof-of-undefined/71506 "2016-11-28T01:47:00Z")\ **Posts on this page:** 1\ **Showing post:** 17
**Author:** ![nilton\_felicio](https://sea1.discourse-cdn.com/ionicframework/user_avatar/forum.ionicframework.com/nilton_felicio/32/100637_2.png) [@nilton\_felicio](https://forum.ionicframework.com/u/nilton_felicio)\ **Post date:** [November 29, 2016, 2:59am UTC](https://forum.ionicframework.com/t/build-dev-failed-cannot-read-property-indexof-of-undefined/71506/17 "2016-11-29T02:59:17Z")
Shocoben, you’re my hero. Good question. Why does angularfire2 install a firebase folder inside your node\_module? The question: To use p firebase service (I never understood this either) we must install in that order: Npm install firebase angularfire2 --save After Shocoben opened my eye: firebase is doubled. 1 - within node\_module 1 - within angularfire2 / node\_module Solution: In node\_module / angularfire2 / node\_module / =\> delete the firebase folder. WORKED FOR ME - Thank you very much Shocoben --- _[View the full topic](https://forum.ionicframework.com/t/build-dev-failed-cannot-read-property-indexof-of-undefined/71506)._