How to make a specific div move with arrow keys (specified by button clicked)

I have 2 divs (#1 and #2) and two buttons. When a button is clicked, it should select a div to move and when the arrow keys are pressed, this div should move. The other should remain in its place. If the other button is clicked, the div that had previously moved should remain in its new position and the newly selected div should move along with the arrow keys.

.counter {
                border-radius:50%;
                width:20px;
                height:20px;
                position:absolute;
                transition:top linear 0.6s, left linear 0.6s;
                font-size:20px;
                font-weight:bold;
                text-align:center;
                padding:20px;
                top: 525px;
                left: 60px;
                background-color:red;
            }

<button onclick="one">Move One</button>
           <button onclick="two">Move Two</button>
           <div class="counter" id="1" >1</div>
           <div class="counter" id="2">2</div>

 var go = "1"
               function one() {
                   go = "1"
               }
               function two() {
                   go = "2"
               }

document.onkeydown = detectKey;
        function detectKey(e) {
    
        var posLeft = document.getElementById('').offsetLeft
        var posTop = document.getElementById('').offsetTop
        
            if (e.keyCode == '39') {
                if (go === "1") {
        document.getElementById('1').style.left  = (posLeft+150)+"px"
        }  
            if (e.keyCode == '38') {
        document.getElementById('1').style.top  = (posTop-150)+"px"
        }
            }
            
            if (e.keyCode == '39') {
                if (go === "2") {
        document.getElementById('2').style.left  = (posLeft+150)+"px"
        }  
            if (e.keyCode == '38') {
        document.getElementById('2').style.top  = (posTop-150)+"px"
        }
            }
    }