KeyMap - Manage maps of handlers for key events
var rules = { // attach handlers to specific keys RETURN: function(event){doSomethingWith(event)}, C_DOWN: ctrlArrowDownHandler, C_S_F7: ctrlShiftF7Handler, // special rules using regular expressions REGEX: [ ["", /^[0-9]$/, digitHandler ], ["C_", /^[aeiou]$/i, ctrlVowelHandler] ], // use Ctrl-X as a prefix for another set of rules C_X: KeyMap.Prefix({R: ctrlX_R_handler, 4: ctrlX_4_handler}) }; // create a keymap object var aKeyMap = new KeyMap(rules); // attach the corresponding handler to the keydown event (on document) aKeyMap.observe("keydown"); // other way to attach : manually insert handler document.onkeydown = aKeyMap.eventHandler({preventDefault: true, ignoreShift : true}); // dynamically change the map aKeyMap.rules.push(new_rules); // idem, temporarily ignore all keys aKeyMap.rules.push(KeyMap.MapAllKeys(function(){})); // back to previous handling state aKeyMap.rules.pop();
aKeyMap.destroy();
This method will remove the keymap handler attached the element/document. Call this method when the concerned element is removed from the DOM or to deactivate the keymap handler.
Provides an abstraction layer for associating handlers with HTML key events, in a browser-independent way.
A keymap is a stack of collections of rules. Each rule has a key specification or a regexp specification, and a handler to be called whenever the specification is met. The keymap object as a whole can then be registered as a usual HTML event handler associated to some DOM element (most often the document element), and will dispatch key events to appropriate handlers.
Key specifications look like A (key 'A'), C_S_A (control-shift-A), A_DELETE (alt-Delete). They are formed from :
For printable characters, the keyname is just that character; for special editing keys such as backspace, arrow up, etc., names are taken from the following list of builtins :
BACKSPACE ESCAPE TAB RETURN LINEFEED SPACE PAGE_UP PAGE_DOWN END HOME LEFT UP RIGHT DOWN INSERT DELETE PAUSE WINDOWS PRINT_SCREEN CAPS_LOCK NUM_LOCK SCROLL_LOCK F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 CTRL SHIFT ALT
Modifiers are specified through prefixes C_, S_ and A_, corresponding to key modifiers control, shift and alt. Several prefixes may be combined, but must appear in the order just given (so for example S_C_A would be illegal).
Alternatively, key specifications may also formed from key codes instead of key names, so for example C_13 is equivalent to C_RETURN. For key codes 0-9, and additional '0' is required to avoid confusion with digits: so C_09 is equivalent to C_TAB, while C_9 means "control-numeric 9".
C_13
C_RETURN
C_09
C_TAB
C_9
In addition, keymap objects can also manage regex rules that cover several possible key events; details are given below.
Following the W3C event model, handlers called from the keymap object receive an event object as argument. This is the usual HTML event object, augmented with two properties keyName and keyModifiers, computed according to the specifications given above. So for example a simple handler can be
keyName
keyModifiers
var myHandler = function (event) { alert(event.keyName + " was pressed with modifiers " + event.keyModifiers); }
Further propagation of the event to other handlers is cancelled by default : W3C methods event.stopPropagation() and event.preventDefault() are called automatically by the keymap object (or, if running under Microsoft Internet Explorer, property cancelBubble is set to true and and property returnValue is set to false). This default behaviour can be disabled if necessary, as explained below.
event.stopPropagation()
event.preventDefault()
cancelBubble
returnValue
Keymaps may be attached to HTML elements on the keydown, keypress or keyup event types. Choosing the proper event type is important, as it affects not only the time at which events are fired, but also the returned keycodes :
keydown
keypress
keyup
These are "low-level" event types that capture almost every key on the keyboard, including special keys like ESCAPE, F1, PAGE UP, etc. Returned key codes remain at a raw level, i.e. they are not translated into characters. This means that if Shift-1 is marked on your keyboard as an exclamation mark, a plus sign, or some other special character, you will not receive that keycode when capturing keydown events : rather, you will receive keycode 49 (ASCII character '1'). Similarly, all letters are received as uppercase.
By contrast, the keypress event type is higher-level in that it performs the translation from keys to characters, according to your specific keyboard. However, this event type only fires for printable characters, so you cannot observe keypress if you intend to capture special keys such as arrow keys, function keys, etc.
In theory, attributes such as onkeydown or onkeypress may be used with most HTML elements; but in practice, most of them will actually never fire the key events! So the most common and most sensible way for capturing key events is to attach to the document element.
onkeydown
onkeypress
document
Events keypress and keydown will repeat if the key is held down.
In order to attach the keymap to an element, you can either use the supplied "observe" method, or call the "eventHandler" method to get the keymap event handler, and then use your favorite technique to attach that handler to an element.
KeyMap
var myKeyMap = new KeyMap(rules);
Constructor for a keymap object.
The rules argument is a map from key specifications to handlers, like for example
{ A: function() {alert("pressed 'A'");}, S_TAB: function() {alert("pressed 'Shift-Tab'");}, CTRL: function() {alert("pressed the 'Ctrl' key");}, 10: function() {alert("pressed 'Linefeed' or maybe 'Ctrl-Return'");} }
Each key specification in the map corresponds to exacly one key combination, so for example S_TAB will not fire if the user pressed Ctrl-Shift-Tab.
S_TAB
Ctrl-Shift-Tab
For situations where several key combination will fire the same handler, you can insert a REGEX entry in the map. This should be an array of triplets, where each triplet is of shape [modifiers, regex, handler], like for example
REGEX
[modifiers, regex, handler]
var regexRules = [["C_", "[0-9]", myCtrlDigitHandler], ["C_S_", /^[AEIOU]$/, myCtrlShiftVowelHandler], [null, "RETURN|TAB|ESCAPE", someOtherHandler] ];
Whenever a key event is received, it is converted into a keyname, and then that keynames is compared against the regex rules, in order : the first rule that matches calls the corresponding handler and terminates the event handling process.
More specifically, the members of rule triplets are :
A string specifiying the key modifiers for which the rule will fire; the string a concatenation of C_, S_ and A_, as explained above. An empty string means that the rule only fires when no modifiers are pressed. By contrast, a null value specifies that modifiers are ignored (the rule fires in any case).
null
Either a string containing a regular expression, or an already built Javascript RegExp object. Strings will be automatically converted to regular expressions, with start anchor ^ and end anchor $ automatically added. If you supply an already built RegExp object, make sure to deal properly with the anchors; otherwise the rule might fire in unexpected cases (for example the plain regex /[AEIOU]/ would match any builtin keyname like RETURN or ESCAPE, which is probably not the intended meaning of the rule).
^
$
/[AEIOU]/
RETURN
ESCAPE
The function to be called when the rule succeeds.
An ANTIREGEX entry in the map works exactly like a REGEX, except that the handler is called when the regex does not match. This is useful if you want to catch most key events, except a given set.
ANTIREGEX
eventHandler
document.onkeydown = aKeyMap.eventHandler(options);
Generates an event handler that can be attached to an HTML element. This method is called internally by the "observe" method. Use eventHandler directly if you need fine control on how the handler is attached to the dynamic HTML model.
The options argument is optional. If present, it should be an inline object containing truth values for the following keys :
options
ignoreCtrl
ignore the Ctrl keyboard modifier
Ctrl
ignoreShift
ignore the Shift keyboard modifier
Shift
ignoreAlt
ignore the Alt keyboard modifier
Alt
stopPropagation
stop propagation of the event
preventDefault
prevent default navigator behaviour on that event
For example if ignoreCtrl is true, then the key specification "C_S_TAB" would never fire, because Ctrl-Shift-TAB key events would be encoded merely as "S_TAB".
"C_S_TAB"
"S_TAB"
observe
aKeyMap.observe(eventType, htmlElement, options);
This is the preferred way for attaching the keymap object to an HTML element, on a given event type (keydown, keypress or keyup). Arguments are optional. The default event type is "keydown", and the default element is document.
"keydown"
Options are passed to the "eventHandler" method. If not explicitly given, the options default to undefined except for event type keypress, where ignoreShift defaults to true. The reason is that the Shift modifier heavily depends on which keyboard the user is using, and often the user really has no choice on pressing or not the Shift key (this would generate a different keycode). So it makes sense to just stop paying attention to the Shift key for keypress events.
undefined
true
rules
aKeyMap.rules.push(new_rules); aKeyMap.rules.pop();
A DHTML application may need to temporarily change the key handlers (for example when switching from navigation mode to editing mode). Therefore, a keymap object actually holds a stack of rules and publishes this stack in its rules property. Rules pushed on top of that stack will take precedence over pre-existing rules; conversely, popping from the stack restores the keymap to its previous state.
MapAllKeys
// grab all keys aKeyMap.rules.push(KeyMap.MapAllKeys(my_handler)); // ignore all keys aKeyMap.rules.push(KeyMap.MapAllKeys(function (){}));
Convenience function to build a regex rule that matches all keys.
Prefix
main_rules = {C_X: KeyMap.Prefix({R: ctrlX_R_handler, 4: ctrlX_4_handler})};
Specifies that a key (here Ctrl-X) is a prefix to another set of rules : the next key event will be passed to these rules, and after that the main rules resumes normal behaviour. Hence you can attach handlers to sequences of keys, like for example in Emacs.
Ctrl-X
To install Alien::GvaScript, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Alien::GvaScript
CPAN shell
perl -MCPAN -e shell install Alien::GvaScript
For more information on module installation, please visit the detailed CPAN module installation guide.