how to hide previous markers when new markers added in google map javascript api

javascript php html

PHP Snippet 1:

const THRESHOLD = 3 // up to 3 active markers
let list = [] // list of markers

const onAddMarker = marker => {

    // init marker
    let marker = new google.maps.Marker([...opts]) 

    // push marker to list
    list.push(marker)

    // check list length and remove oldest marker (if needed)
    if (list.length > THRESHOLD)
        list.shift().setMap(null)
    
}