[рони]

AMATORx,

let ml = 0, timer;
        function move(){
            let blockOne = document.getElementById('one');
            ml = ml + 10;
            blockOne.style.marginLeft = ml + 'px';
            timer = setTimeout(move, 50);
        }
        document.getElementById('start').onclick = move;
        document.getElementById('stop').onclick = function(){
            clearTimeout(timer);
        }
        onload = move;