App performance optimalizations

Iam finishing with app iam developing, but i would like it to be a little faster in loading time and even in reaction. Make it feel more smooth. Are there any best practises for optimizing ionic app? Maybe some things in code that should be avoided(for example what about foreach on big arrays and so on), or are there any other tricks, beside building apps with --prod flag?

And maybe another question, are there any tools to analyze apps performance and which methods or components are problem?

Two things I’ve done to make them more performant in terms of reaction time.

For iOS, speed up page transitions. Amazing how that fraction of time feels so much more performant.
If you want to know just shout.

For iOS and Android, for list item buttons, wrap the function in a setTimeout of 100ms. That delay separates the animation from the action so you’re not clicking with nothing happening. Feels way nicer.