var input = document.querySelector("#input");

input.addEventListener('keydown', showKey);

​

function showKey(e){

  console.log(e.keyCode);

  switch(e.keyCode){

    case 13:

      console.log('Enter');

      break;

    case 49:

      console.log('1');

      break;

    case 50:

      console.log('2');

      break;

    case 51:

      console.log('3');

      break;

  }

}