如何使用一个按钮在谷歌地图上显示/隐藏标记数组

Trying to make one button to show/hide markers on the map. Code creates an array of markers out of array of locations and initially shows them on the map. When I click the button to hide the markers it hides them but when I click it again to show the markers it does nothing. I'm just a beginner but I've been stuck on this for a long time. Please help.Trying to make one button to show/hide markers