Javascript/jQuery Keypress logging

I would like to be able to log the key presses on a specific page, trying to implement an 'Easter egg' type functionality where when the correct keys ar开发者_运维问答e pressed in the correct order it triggers and event.

Can anyone give me any pointers?

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Well, even though another answer has been accepted, I'm going to throw one out there anyway.

$(document).ready(function() {

    var easterEgg = 'egg';
    var eggLength = easterEgg.length;
    var keyHistory = '';
    var match;
        $(document).keypress(function(e) {
            keyHistory += String.fromCharCode(e.which)
            match = keyHistory.match(easterEgg); 
            if(match) {
                alert(match);
                keyHistory = match =  '';
            } else if (keyHistory.length > 30) {
                keyHistory = keyHistory.substr((keyHistory.length - eggLength - 1));
            }
        });
});

When you ultimately type 'egg' (for this example), you will get an alert, and the key history will reset.

EDIT: Updated the code to truncate the string if it gets too long.

---

In such circumstances it might also be useful to be able to check for the ctl/alt/shift keys:

if (e.altKey) {
}

if (e.ctrlKey) {
}

if (e.shiftKey) {
}

For keypress codes, the following object literal should help:

var Key =
{
    BACKSPACE: 8,
    TAB: 9,
    ENTER: 13,
    ESC: 27,
    PAGEUP: 33,
    PAGEDOWN: 34,
    END: 35,
    HOME: 36,
    LEFT: 37,
    UP: 38,
    RIGHT: 39,
    DOWN: 40,
    HELP: 47,
    H: 72,
    K: 75,
    N: 78,
    R: 82,
    NUMERIC_PLUS: 107,
    F1: 112,
    F2: 113,
    F3: 114,
    F4: 115,
    F5: 116,
    F6: 117,
    F7: 118,
    F8: 119,
    F9: 120,
    F10: 121,
    F11: 122,
    F12: 123,
    PLUS: 187,
    MINUS: 189,
    V: 86
}

So instead of:

  switch(event.keyCode) { 
    case 40: 
      keypresses.push('down'); 
    break; 
    case 38: 
      keypresses.push('up'); 
  } 

We can say:

switch(event.keyCode) { 
    case Key.DOWN: 
        keypresses.push('down'); 
        break; 
    case Key.UP: 
        keypresses.push('up'); 
        break; 
} 

This promotes self documenting code, and is more readable and maintainable.

---

I'm not sure of the exact keypress codes, I borrowed from Hans Kov's answer. I would use an array like a stack and just push a new keypress onto the stack, then pop them off to check for correct order.

<script type="text/javascript">
  var keypresses = [];
    $(document).ready(function() {
      body.bind('keypress', function(event) {
        switch(event.keyCode) {
          case 40:
            keypresses.push('down');
          break;
          case 38:
            keypresses.push('up');
        }
  
        checkForEasterEgg(keypresses);
      });
    });
  
    function checkForEasterEgg(keyArray) {
      var length = keyArray.length;
      for(var i = 0; i < length; i++) {
        // using keyArray.pop(), check if order matches up up down down left right left right b a
        if (easterEggPassed) {
          console.log('30 lives, woohoo!');
        }
      }
    }
</script>

---

I have earlier used this code to use the up/down arrows to scroll through a list, it should be relativly easy to extend this to check for a certain key combo.

$("#SearchInput").keydown(function(e){
  switch(e.which) { 
     // User pressed "up" arrow
     case 38:
        navigate('up');
     break;
     // User pressed "down" arrow
     case 40:
        navigate('down');
     break;
     // User pressed "enter"
     case 13:
        if(currentUrl != '') {
           window.location = currentUrl;
        }
     break;
  }

---

Using jQuery:

$(document).keyup( function(e) {
    if (e.keyCode == 27) {
        alert("You pressed escape");
    }
});

This captures key presses on the whole page not just a specific element.

This blog post details how to capture CTRL+Key shortcuts.

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here's an easy way to require the ctrl key to be held down while the user enters a sequence of characters. a bit easier than some of the responses. in the case below pressing and holding ctrl key while typing "quack" (no quotes) will trigger the alert. hth someone, someday.

     var easterEgg = [81, 85, 65, 67, 75]; //quack
     var eggLength = easterEgg.length;
     var currentPosition = 0;
     $(document).keydown(function (e) {
         if (e.ctrlKey && e.keyCode == easterEgg[currentPosition]) {
             e.preventDefault();
             if (++currentPosition == eggLength) {
                 currentPosition = 0;
                 alert('oh yeah, right there');
             }
         } else {
             currentPosition = 0;
         }
     });

---

This maybe?

var seq = "rainbow"
var input = ""
window.addEventListener("keypress", function(e) {
    input += String.fromCharCode(e.keyCode)

    for (var i = 0; i < seq.length; i++) {
        if (input[i] != seq[i] && input[i] != undefined) {
            input = ""
        }
    }

    if (input == seq) {
        alert("EASTER EGG!")

        input = ""
    }
})