The source code

    /**
     * @class Ext.KeyNav
     * Provides a convenient wrapper for normalized keyboard navigation.  KeyNav allows you to bind
     * navigation keys to function calls that will get called when the keys are pressed, providing an easy
     * way to implement custom navigation schemes for any UI component.
     * The following are all of the possible keys that can be implemented: enter, left, right, up, down, tab, esc,
     * pageUp, pageDown, del, home, end.  Usage:

    var nav = new Ext.KeyNav("my-element", {
        "left" : function(e){
            this.moveLeft(e.ctrlKey);
        },
        "right" : function(e){
            this.moveRight(e.ctrlKey);
        },
        "enter" : function(e){
            this.save();
        },
        scope : this
    });

     * @constructor
     * @param {Mixed} el The element to bind to
     * @param {Object} config The config
     */
    Ext.KeyNav = function(el, config){
        this.el = Ext.get(el);
        Ext.apply(this, config);
        if(!this.disabled){
            this.disabled = true;
            this.enable();
        }
    };

    Ext.KeyNav.prototype = {
        /**
         * @cfg {Boolean} disabled
         * True to disable this KeyNav instance (defaults to false)
         */
        disabled : false,
        /**
         * @cfg {String} defaultEventAction
         * The method to call on the {@link Ext.EventObject} after this KeyNav intercepts a key.  Valid values are
         * {@link Ext.EventObject#stopEvent}, {@link Ext.EventObject#preventDefault} and
         * {@link Ext.EventObject#stopPropagation} (defaults to 'stopEvent')
         */
        defaultEventAction: "stopEvent",
        /**
         * @cfg {Boolean} forceKeyDown
         * Handle the keydown event instead of keypress (defaults to false).  KeyNav automatically does this for IE since
         * IE does not propagate special keys on keypress, but setting this to true will force other browsers to also
         * handle keydown instead of keypress.
         */
        forceKeyDown : false,

        // private
        prepareEvent : function(e){
            var k = e.getKey();
            var h = this.keyToHandler[k];
            if(Ext.isSafari2 && h && k >= 37 && k <= 40){
                e.stopEvent();
            }
        },

        // private
        relay : function(e){
            var k = e.getKey();
            var h = this.keyToHandler[k];
            if(h && this[h]){
                if(this.doRelay(e, this[h], h) !== true){
                    e[this.defaultEventAction]();
                }
            }
        },

        // private
        doRelay : function(e, h, hname){
            return h.call(this.scope || this, e);
        },

        // possible handlers
        enter : false,
        left : false,
        right : false,
        up : false,
        down : false,
        tab : false,
        esc : false,
        pageUp : false,
        pageDown : false,
        del : false,
        home : false,
        end : false,

        // quick lookup hash
        keyToHandler : {
            37 : "left",
            39 : "right",
            38 : "up",
            40 : "down",
            33 : "pageUp",
            34 : "pageDown",
            46 : "del",
            36 : "home",
            35 : "end",
            13 : "enter",
            27 : "esc",
            9  : "tab"
        },

    	/**
    	 * Enable this KeyNav
    	 */
    	enable: function(){
    		if(this.disabled){
                // ie won't do special keys on keypress, no one else will repeat keys with keydown
                // the EventObject will normalize Safari automatically
                if(this.isKeydown()){
                    this.el.on("keydown", this.relay,  this);
                }else{
                    this.el.on("keydown", this.prepareEvent,  this);
                    this.el.on("keypress", this.relay,  this);
                }
    		    this.disabled = false;
    		}
    	},

    	/**
    	 * Disable this KeyNav
    	 */
    	disable: function(){
    		if(!this.disabled){
    		    if(this.isKeydown()){
                    this.el.un("keydown", this.relay, this);
                }else{
                    this.el.un("keydown", this.prepareEvent, this);
                    this.el.un("keypress", this.relay, this);
                }
    		    this.disabled = true;
    		}
    	},

        /**
         * Convenience function for setting disabled/enabled by boolean.
         * @param {Boolean} disabled
         */
        setDisabled : function(disabled){
            this[disabled ? "disable" : "enable"]();
        },

        // private
        isKeydown: function(){
            return this.forceKeyDown || Ext.EventManager.useKeydown;
        }
    };