var key = event.which || event.keyCode || event.charCode;

if(key == 8) alert('backspace');

$('#content').bind('input', function(event){

    var text = $(this).val(),
        key = event.which || event.keyCode || event.charCode;

    if(key == 8){
      // here I want to ignore backspace and del
    }

    // here I'm doing my stuff
    var new_text = 'bla bla'+text;
    $(this).val(new_text);
  });

var input = document.getElementById('myInput');

input.onkeydown = function() {
    var key = event.keyCode || event.charCode;

    if( key == 8 || key == 46 )
        return false;
};

jQuery(function($) {
  var input = $('#myInput');
  input.on('keydown', function() {
    var key = event.keyCode || event.charCode;

    if( key == 8 || key == 46 )
        return false;
  });
});

jQuery('#input').on('keydown', function(e) {
    if( e.which == 8 || e.which == 46 ) return false;
});