var userInput = prompt("Enter a String:");

var alphabetPosition = function(str) {
  var numTable = {
    A : 1,
    B : 2,
    C : 3,
    D : 4,
    E : 5,
    F : 6,
    G : 7,
    H : 8,
    I : 9,
    J : 10,
    K : 11,
    L : 12,
    M : 13,
    N : 14,
    O : 15,
    P : 16,
    Q : 17,
    R : 18,
    S : 19,
    T : 20,
    U : 21,
    V : 22,
    W : 23,
    X : 24,
    Y : 25,
    Z : 26
  };

  var upper = str.toUpperCase();
  var result = "";
  for (var i = 0 ; i < upper.length; i += 1) {
    var now = numTable[upper[i]];
    if (now !== undefined) {
      result += now + " ";
    }
  }
  return result;
}

console.log(alphabetPosition(userInput));