value doesn`t work

value does not work. what is wrong?

equal.addEventListener('click', function (e) {
    if (screen.value === '') {
      screen.value = "";
    } else {
      let answer = eval(screen.value);
      screen.value = answer;
    }

let answer = eval(screen.value);

Uncaught SyntaxError: Invalid or unexpected token
    at HTMLButtonElement.<anonymous> (app.js:47:32)