Calculator Button will delete single digits but won’t allow for more numbers to be added

The delete button will function properly, as far as delete single digits in a set of numbers, but if the numbers are still on the display screen – after then hitting delete with a couple numbers still on the screen – it won’t allow me to add new numbers to the current screen.

let operator = '';
let previousValue='';
let currentValue='';

//let deleteBtn = document.getElementById('delete')


document.addEventListener("DOMContentLoaded", function(){
    let clear = document.querySelector('.clear');
    let equal = document.querySelector(".equal");
    let backspace = document.querySelector('.delete');
    
    

    //let deletes = document.querySelector('.delete');
    
    //let deletebtn = del[0]

    let numbers = document.querySelectorAll(".number");
    let operators = document.querySelectorAll(".operator");

    let previousScreen = document.querySelector('.previous');
    let currentScreen = document.querySelector('.current');

    numbers.forEach((number) => number.addEventListener("click", function(e){
          handleNumber(e.target.textContent)
          currentScreen.textContent = currentValue;
    }))

    operators.forEach((op) => op.addEventListener("click", function(e){

        handleOperator(e.target.textContent)
        previousScreen.textContent = previousValue + "" + operator;
        currentScreen.textContent = currentValue;
    }))

    clear.addEventListener("click", function(){
        previousValue = '';
        currentValue = '';
        operator = '';
        previousScreen.textContent = currentValue;
        currentScreen.textContent = currentValue;
    })

    equal.addEventListener("click", function(){
        answer();
        previousScreen.textContent='';
        currentScreen.textContent = previousValue;
    })


   

    backspace.addEventListener("click", function(){

        let temp
        if (currentValue === 0){
        currentValue=0;
        temp = currentValue;
        
        
    }

        
        //temp = currentValue.toString().slice(0,-1)

        else {
           temp =  currentValue.toString().slice(0,-1)

        }
        
        if (temp ===''|| temp === ''){
            temp = '';
            currentValue = temp;
            upDateDisplay();


       }
        else {
            currentValue = parseFloat(temp)
            upDateDisplay();

        }
        
function upDateDisplay(){
    currentScreen.textContent = currentValue;
    previousScreen.textContent = previousValue;

}
        
        
        
      })

    

   
   

})

function handleNumber(num){
    if(currentValue.length <= 10){
    currentValue += num;
    }
}

function handleOperator(op){
    operator= op;
    previousValue = currentValue;
    currentValue="";
}

//function back(backspace){

   // currentScreen('backspace', -1);

//}

function answer(){

    previousValue = Number(previousValue);
    currentValue = Number(currentValue);

    if(operator === "+"){
        previousValue += currentValue;
    } else if (operator === "^") {
        previousValue **= currentValue;
    } else if(operator === "-"){
        previousValue -= currentValue;
    } else if(operator === "x"){
        previousValue *= currentValue;
    } else {
        previousValue /= currentValue;
    }

    previousValue = round(previousValue);
    previousValue = previousValue.toString();
    currentValue = previousValue.toString();
}

  function round(num){
   return Math.round(num * 1000) / 1000;
}

I did mess around with some of the javascript code shown but it only lead to other errors without fixing my current problem.