javascript - 无法覆盖键盘 ALT 修饰符

Question

我正在编写一个 Javascript 类来处理击键和击键组合。例如，以下将为 SHIFT 键添加回调。

MYAPP.Keyboard.instance().observe(
    MYAPP.Keyboard.type.KEYDOWN,
    MYAPP.Keyboard.key.SHIFT,
    function() {
        $$('body').first().addClassName('keyboardHintShow');
    }
);

SHIFT+F 的示例是:

MYAPP.Keyboard.instance().observe(
    MYAPP.Keyboard.type.KEYUP,
    [MYAPP.Keyboard.key.F, MYAPP.Keyboard.key.SHIFT],
    function() {
        MYAPP.Broadcast.instance().signal('file');
    }
);  

到目前为止，这在 Firefox 中运行良好，但当我尝试使用 ALT 作为修饰符时却不行。出现两个问题。 1) 事件传播没有停止，因此弹出 Firefox 的文件菜单。 2)释放ALT和F后，只有F的onKeyUp触发，所以ALT的状态是错误的.是什么让 ALT 与 SHIFT 如此不同？

完整代码如下:

MYAPP.Keyboard = Class.create({

/*******************************************************************************
PUBLIC PUBLIC PUBLIC PUBLIC PUBLIC PUBLIC PUBLIC PUBLIC PUBLIC PUBLIC PUBLIC PUB
*******************************************************************************/

    /**
     * @return pointer
     */
    initialize: function() {
        this.downKeys = new Hash();
        this.observers = new Hash();

        document.observe(
            'keydown',
            this.onKeyDown.bind(this)
        );

        document.observe(
            'keyup',
            this.onKeyUp.bind(this)
        );
    },

    /**
     * @param MYAPP.Keyboard.type type
     * @param MYAPP.Keyboard.key | array of MYAPP.Keyboard.key keys
     * @param void function() callback
     * @return void
     */
    observe: function(type, keys, callback) {
        var main;
        var modifiers;

        if (typeof(keys) === 'number') {
            main = keys;
            modifiers = [];
        } else {
            main = keys.first();
            modifiers = keys.slice(1);
        }

        if (this.observers.get(type) === undefined) {
            this.observers.set(type, new Hash());
        }

        this.observers.get(type).set(
            main, {
                modifiers: modifiers,
                callback: callback
            }
        );
    },

    /**
     * @param MYAPP.Keyboard.type type
     * @param MYAPP.Keyboard.key
     * @return void
     */
    stopObserving: function(type, key) {
        this.observers.get(type).unset(key);
    },

/*******************************************************************************
PRIVATE PRIVATE PRIVATE PRIVATE PRIVATE PRIVATE PRIVATE PRIVATE PRIVATE PRIVATE 
*******************************************************************************/

    /**
     * @param Event event
     * @return void
     */
    onKeyDown: function(event) {
        if (this.downKeys.get(event.keyCode) === true) {
            return;
        }

        this.downKeys.set(event.keyCode, true);

        var downObservers = this.observers.get(MYAPP.Keyboard.type.KEYDOWN);
        if (downObservers !== undefined) {
            this.runCallback(downObservers, event);
        }
        return false;
    },

    /**
     * @param Event event
     * @return void
     */
    onKeyUp: function(event) {
        this.downKeys.set(event.keyCode, false);

        var downObservers = this.observers.get(MYAPP.Keyboard.type.KEYUP);
        if (downObservers !== undefined) {
            this.runCallback(downObservers, event);
        }
        return false;
    },

    /**
     * @param Hash observers
     * @param Event event
     * @return void
     */
    runCallback: function(observers, event) {
        var overrideBrowser = false;
        var order = observers.get(event.keyCode);
        if (order !== undefined) {
            if (order.modifiers.size() === 0) {
                order.callback();
                Event.stop(event);
            } else {
                for (var i = 0; i < order.modifiers.size(); i++) {
                    var modifierStatus = this.downKeys.get(order.modifiers[i]);
                    if (modifierStatus === undefined || modifierStatus === false) {
                        return;
                    }
                    order.callback();
                    Event.stop(event);
                }
            }
        }
    }
});

/*******************************************************************************
STATIC STATIC STATIC STATIC STATIC STATIC STATIC STATIC STATIC STATIC STATIC STA
*******************************************************************************/

/**
 * @return Keyboard instance
 */
MYAPP.Keyboard.instance = function() {
    if (typeof(MYAPP.keyboard) === 'undefined') {
        MYAPP.keyboard = new MYAPP.Keyboard();
    }
    return MYAPP.keyboard;
};

/**
 * Event type
 */
MYAPP.Keyboard.type = {
    KEYUP: 0,
    KEYDOWN: 1 
};

/**
 * Keycodes for various keys.
 */
MYAPP.Keyboard.key = {
    SHIFT: 16,
    CTRL: 17,
    ALT: 18,
    A: 65,
    B: 66,
    C: 67,
    D: 68,
    E: 69,
    F: 70,
    G: 71,
    H: 72,
    I: 73,
    J: 74,
    K: 75,
    L: 76,
    M: 77,
    N: 78,
    O: 79,
    P: 80,
    Q: 81,
    R: 82,
    S: 83,
    T: 84,
    U: 85,
    V: 86,
    W: 87,
    X: 88,
    Y: 89,
    Z: 90
};

Answer 1

This可能会有所帮助作为一个例子。在页面底部，作者声称他的脚本覆盖了所有修饰符 - Ctrl、Alt、Shift、Meta。希望这能以某种方式有所帮助。