如何动态设置最大缩放级别以适应google-map中的标记列表？

This is my code, I've used angular-google-map API for it. Here I try to set the zoom level of 20 statically, but as per my requirement, in some place I need 17, somewhere 18 zoom level. So I want to dynamically generate the maximum possible zoom level to fit all the markers.This is my code, I've used angular-google-map A