I have problem with dragging elements in html

I am making page like google maps with html, css, javascript so I want to make page draggable.

        let newX = 0, newY = 0, startX = 0, startY = 0;

        const map = document.getElementsByClassName('world-map')[0]

        map.addEventListener('mousedown', mouseDown)

        function mouseDown(e) {
            startX = e.clientX
            startY = e.clientY

            document.addEventListener('mousemove', mouseMove)
            document.addEventListener('mouseup', mouseUp)
        }

        function mouseMove(e){
        newX = startX - e.clientX 
        newY = startY - e.clientY 
    
        startX = e.clientX
        startY = e.clientY

        map.style.left = startX + 'px'
        map.style.top = startY + 'px'

        }
        
        function mouseUp(e) {
            document.removeEventListener('mousemove', mouseMove)
        }

I tried this but it moves back to start point(0,0) after mouseup and then

        let newX = 0, newY = 0, startX = 0, startY = 0;

        const map = document.getElementsByClassName('world-map')[0]

        map.addEventListener('mousedown', mouseDown)

        function mouseDown(e) {
            startX = e.clientX
            startY = e.clientY

            document.addEventListener('mousemove', mouseMove)
            document.addEventListener('mouseup', mouseUp)
        }

        function mouseMove(e){
        newX = startX - e.clientX 
        newY = startY - e.clientY 
    
        startX = e.clientX
        startY = e.clientY

        map.style.top = (map.offsetTop - startY) + 'px'
        map.style.left = (map.offsetLeft - startX) + 'px'

        }
        
        function mouseUp(e) {
            document.removeEventListener('mousemove', mouseMove)
        }

tried this but it doesn’t even move.

Element world-map’s css is ‘position:absolute’

I think I need to update a new x,y in variables after moving so tried several ways but it doesn’t worked.
Is there any possible way to make it?
Sorry for my bad english.