How to remove the first marker after I search again as location center on google maps javascript?

can help me about my problem. I want to search location center of the city, the problem is when i choose one of all cities, example i choose South Jakarta city, and then marker will display the city, after that, when i choose again, why the marker show double or so on of marker? Like this..correct result, this is correct. But when i want to search another city again, the picture will show like this.. incorrect result This is link from my javascript code... https://s.id/29-uk

please if you understand what i mean.