I am having issues with markers overlapping, please do not down vote as I am not highly schooled in javascript also I have looked at the different answers offered on stackoverfl
If you don't want markers overlapping, you'll probably need to use google-maps-utility-library-v3. It has a feature called Marker Clusterer, which basically allows you to put nearby markers into one singular marker. It can be configured so that these markers reappear as separate entities once the user has zoomed in far enough. Here's a demo.