Extremely slow on ios

I have built a simple application in ionic with Pushwoosh notifications. The application build works fine on android devices but super-slow on ios - emulator and actual device. I have to click on a button 9-12 times before it responds. I cannot understand why is it so? Functionality wise everything is working fine. Just that everything is very slow.

Here’s the code:
https://github.com/kirobo/ionic