Yahoo! UI Library

Event Utility  2.5.2

Yahoo! UI Library > event > KeyListener.js (source view)

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/**
* KeyListener is a utility that provides an easy interface for listening for
* keydown/keyup events fired against DOM elements.
* @namespace YAHOO.util
* @class KeyListener
* @constructor
* @param {HTMLElement} attachTo The element or element ID to which the key 
*                               event should be attached
* @param {String}      attachTo The element or element ID to which the key
*                               event should be attached
* @param {Object}      keyData  The object literal representing the key(s) 
*                               to detect. Possible attributes are 
*                               shift(boolean), alt(boolean), ctrl(boolean) 
*                               and keys(either an int or an array of ints 
*                               representing keycodes).
* @param {Function}    handler  The CustomEvent handler to fire when the 
*                               key event is detected
* @param {Object}      handler  An object literal representing the handler. 
* @param {String}      event    Optional. The event (keydown or keyup) to 
*                               listen for. Defaults automatically to keydown.
*
* @knownissue the "keypress" event is completely broken in Safari 2.x and below.
*             the workaround is use "keydown" for key listening.  However, if
*             it is desired to prevent the default behavior of the keystroke,
*             that can only be done on the keypress event.  This makes key
*             handling quite ugly.
* @knownissue keydown is also broken in Safari 2.x and below for the ESC key.
*             There currently is no workaround other than choosing another
*             key to listen for.
*/
YAHOO.util.KeyListener = function(attachTo, keyData, handler, event) {
    if (!attachTo) {
        YAHOO.log("No attachTo element specified", "error");
    } else if (!keyData) {
        YAHOO.log("No keyData specified", "error");
    } else if (!handler) {
        YAHOO.log("No handler specified", "error");
    } 
    
    if (!event) {
        event = YAHOO.util.KeyListener.KEYDOWN;
    }

    /**
    * The CustomEvent fired internally when a key is pressed
    * @event keyEvent
    * @private
    * @param {Object} keyData The object literal representing the key(s) to 
    *                         detect. Possible attributes are shift(boolean), 
    *                         alt(boolean), ctrl(boolean) and keys(either an 
    *                         int or an array of ints representing keycodes).
    */
    var keyEvent = new YAHOO.util.CustomEvent("keyPressed");
    
    /**
    * The CustomEvent fired when the KeyListener is enabled via the enable() 
    * function
    * @event enabledEvent
    * @param {Object} keyData The object literal representing the key(s) to 
    *                         detect. Possible attributes are shift(boolean), 
    *                         alt(boolean), ctrl(boolean) and keys(either an 
    *                         int or an array of ints representing keycodes).
    */
    this.enabledEvent = new YAHOO.util.CustomEvent("enabled");

    /**
    * The CustomEvent fired when the KeyListener is disabled via the 
    * disable() function
    * @event disabledEvent
    * @param {Object} keyData The object literal representing the key(s) to 
    *                         detect. Possible attributes are shift(boolean), 
    *                         alt(boolean), ctrl(boolean) and keys(either an 
    *                         int or an array of ints representing keycodes).
    */
    this.disabledEvent = new YAHOO.util.CustomEvent("disabled");

    if (typeof attachTo == 'string') {
        attachTo = document.getElementById(attachTo);
    }

    if (typeof handler == 'function') {
        keyEvent.subscribe(handler);
    } else {
        keyEvent.subscribe(handler.fn, handler.scope, handler.correctScope);
    }

    /**
    * Handles the key event when a key is pressed.
    * @method handleKeyPress
    * @param {DOMEvent} e   The keypress DOM event
    * @param {Object}   obj The DOM event scope object
    * @private
    */
    function handleKeyPress(e, obj) {
        if (! keyData.shift) {  
            keyData.shift = false; 
        }
        if (! keyData.alt) {    
            keyData.alt = false;
        }
        if (! keyData.ctrl) {
            keyData.ctrl = false;
        }

        // check held down modifying keys first
        if (e.shiftKey == keyData.shift && 
            e.altKey   == keyData.alt &&
            e.ctrlKey  == keyData.ctrl) { // if we pass this, all modifiers match
            
            var dataItem;

            if (keyData.keys instanceof Array) {
                for (var i=0;i<keyData.keys.length;i++) {
                    dataItem = keyData.keys[i];

                    if (dataItem == e.charCode ) {
                        keyEvent.fire(e.charCode, e);
                        break;
                    } else if (dataItem == e.keyCode) {
                        keyEvent.fire(e.keyCode, e);
                        break;
                    }
                }
            } else {
                dataItem = keyData.keys;
                if (dataItem == e.charCode ) {
                    keyEvent.fire(e.charCode, e);
                } else if (dataItem == e.keyCode) {
                    keyEvent.fire(e.keyCode, e);
                }
            }
        }
    }

    /**
    * Enables the KeyListener by attaching the DOM event listeners to the 
    * target DOM element
    * @method enable
    */
    this.enable = function() {
        if (! this.enabled) {
            YAHOO.util.Event.addListener(attachTo, event, handleKeyPress);
            this.enabledEvent.fire(keyData);
        }
        /**
        * Boolean indicating the enabled/disabled state of the Tooltip
        * @property enabled
        * @type Boolean
        */
        this.enabled = true;
    };

    /**
    * Disables the KeyListener by removing the DOM event listeners from the 
    * target DOM element
    * @method disable
    */
    this.disable = function() {
        if (this.enabled) {
            YAHOO.util.Event.removeListener(attachTo, event, handleKeyPress);
            this.disabledEvent.fire(keyData);
        }
        this.enabled = false;
    };

    /**
    * Returns a String representation of the object.
    * @method toString
    * @return {String}  The string representation of the KeyListener
    */ 
    this.toString = function() {
        return "KeyListener [" + keyData.keys + "] " + attachTo.tagName + 
                (attachTo.id ? "[" + attachTo.id + "]" : "");
    };

};

/**
* Constant representing the DOM "keydown" event.
* @property YAHOO.util.KeyListener.KEYDOWN
* @static
* @final
* @type String
*/
YAHOO.util.KeyListener.KEYDOWN = "keydown";

/**
* Constant representing the DOM "keyup" event.
* @property YAHOO.util.KeyListener.KEYUP
* @static
* @final
* @type String
*/
YAHOO.util.KeyListener.KEYUP = "keyup";

/**
 * keycode constants for a subset of the special keys
 * @property KEY
 * @static
 * @final
 */
YAHOO.util.KeyListener.KEY = {
    ALT          : 18,
    BACK_SPACE   : 8,
    CAPS_LOCK    : 20,
    CONTROL      : 17,
    DELETE       : 46,
    DOWN         : 40,
    END          : 35,
    ENTER        : 13,
    ESCAPE       : 27,
    HOME         : 36,
    LEFT         : 37,
    META         : 224,
    NUM_LOCK     : 144,
    PAGE_DOWN    : 34,
    PAGE_UP      : 33, 
    PAUSE        : 19,
    PRINTSCREEN  : 44,
    RIGHT        : 39,
    SCROLL_LOCK  : 145,
    SHIFT        : 16,
    SPACE        : 32,
    TAB          : 9,
    UP           : 38
};

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