你能给我看一些 Keymap.js 的例子吗，（权威指南）？

Question

function Keymap(bindings) {
    this.map = {};    // Define the key identifier->handler map
    if (bindings) {   // Copy initial bindings into it
        for(name in bindings) this.bind(name, bindings[name]);
    }
}

// Bind the specified key identifier to the specified handler function
Keymap.prototype.bind = function(key, func) {
    this.map[Keymap.normalize(key)] = func;
};

// Delete the binding for the specified key identifier
Keymap.prototype.unbind = function(key) {
    delete this.map[Keymap.normalize(key)];
};

// Install this Keymap on the specified HTML element
Keymap.prototype.install = function(element) {
    // This is the event-handler function
    var keymap = this;
    function handler(event) { return keymap.dispatch(event, element); }

    // Now install it
    if (element.addEventListener)
        element.addEventListener("keydown", handler, false);
    else if (element.attachEvent) 
        element.attachEvent("onkeydown", handler);
};

// This method dispatches key events based on the keymap bindings.
Keymap.prototype.dispatch = function(event, element) {
    // We start off with no modifiers and no key name
    var modifiers = ""
    var keyname = null;

    // Build the modifier string in canonical lowercase alphabetical order.
    if (event.altKey) modifiers += "alt_";      
    if (event.ctrlKey) modifiers += "ctrl_";
    if (event.metaKey) modifiers += "meta_";
    if (event.shiftKey) modifiers += "shift_";

    // The keyname is easy if the DOM Level 3 key property is implemented:
    if (event.key) keyname = event.key;
    // Use the keyIdentifier on Safari and Chrome for function key names
    else if (event.keyIdentifier && event.keyIdentifier.substring(0,2) !== "U+")
        keyname = event.keyIdentifier;
    // Otherwise, use the keyCode property and the code-to-name map below
    else keyname = Keymap.keyCodeToKeyName[event.keyCode];

    // If we couldn't figure out a key name, just return and ignore the event.
    if (!keyname) return;

    // The canonical key id is modifiers plus lowercase key name
    var keyid = modifiers + keyname.toLowerCase();

    // Now see if the key identifier is bound to anything
    var handler = this.map[keyid];

    if (handler) {  // If there is a handler for this key, handle it
        // Invoke the handler function
        var retval = handler.call(element, event, keyid);

        // If the handler returns false, cancel default and prevent bubbling
        if (retval === false) {
            if (event.stopPropagation) event.stopPropagation();  // DOM model
            else event.cancelBubble = true;                      // IE model
            if (event.preventDefault) event.preventDefault();    // DOM
            else event.returnValue = false;                      // IE
        }

        // Return whatever the handler returned
        return retval;
    }
};

// Utility function to convert a key identifier to canonical form.
// On non-Macintosh hardware, we could map "meta" to "ctrl" here, so that
// Meta-C would be "Command-C" on the Mac and "Ctrl-C" everywhere else.
Keymap.normalize = function(keyid) {
    keyid = keyid.toLowerCase();           // Everything lowercase
    var words = keyid.split(/\s+|[\-+_]/); // Split modifiers from name
    var keyname = words.pop();             // keyname is the last word
    keyname = Keymap.aliases[keyname] || keyname; // Is it an alias?
    words.sort();                          // Sort remaining modifiers
    words.push(keyname);                   // Add the normalized name back 
    return words.join("_");                // Concatenate them all
};

Keymap.aliases = {        // Map common key aliases to their "official" 
    "escape":"esc",       // key names used by DOM Level 3 and by 
    "delete":"del",       // the key code to key name map below.
    "return":"enter",     // Both keys and values must be lowercase here.
    "ctrl":"control",
    "space":"spacebar",
    "ins":"insert"
};

// The legacy keyCode property of the keydown event object is not standardized
// But the following values seem to work for most browsers and OSes.
Keymap.keyCodeToKeyName = {
    // Keys with words or arrows on them
    8:"Backspace", 9:"Tab", 13:"Enter", 16:"Shift", 17:"Control", 18:"Alt",
    19:"Pause", 20:"CapsLock", 27:"Esc", 32:"Spacebar", 33:"PageUp",  
    34:"PageDown", 35:"End", 36:"Home", 37:"Left", 38:"Up", 39:"Right",
    40:"Down", 45:"Insert", 46:"Del",

    // Number keys on main keyboard (not keypad)
    48:"0",49:"1",50:"2",51:"3",52:"4",53:"5",54:"6",55:"7",56:"8",57:"9",

    // Letter keys. Note that we don't distinguish upper and lower case
    65:"A", 66:"B", 67:"C", 68:"D", 69:"E", 70:"F", 71:"G", 72:"H", 73:"I",
    74:"J", 75:"K", 76:"L", 77:"M", 78:"N", 79:"O", 80:"P", 81:"Q", 82:"R",
    83:"S", 84:"T", 85:"U", 86:"V", 87:"W", 88:"X", 89:"Y", 90:"Z",

    // Keypad numbers and punctuation keys. (Opera does not support these.)
    96:"0",97:"1",98:"2",99:"3",100:"4",101:"5",102:"6",103:"7",104:"8",105:"9",
    106:"Multiply", 107:"Add", 109:"Subtract", 110:"Decimal", 111:"Divide",

    // Function keys
    112:"F1", 113:"F2", 114:"F3", 115:"F4", 116:"F5", 117:"F6",
    118:"F7", 119:"F8", 120:"F9", 121:"F10", 122:"F11", 123:"F12",
    124:"F13", 125:"F14", 126:"F15", 127:"F16", 128:"F17", 129:"F18",
    130:"F19", 131:"F20", 132:"F21", 133:"F22", 134:"F23", 135:"F24",

    // Punctuation keys that don't require holding down Shift
    // Hyphen is nonportable: FF returns same code as Subtract
    59:";", 61:"=", 186:";", 187:"=", // Firefox and Opera return 59,61 
    188:",", 190:".", 191:"/", 192:"`", 219:"[", 220:"\\", 221:"]", 222:"'"
};

JavaScript：权威指南：6th Keymap.js

Keymap.js：将键事件绑定到处理函数。

这个模块定义了一个 Keymap 类。这个类的一个实例代表一个 键标识符（定义如下）到处理函数的映射。键盘映射 可以安装在 HTML 元素上以处理 keydown 事件。当这样一个 事件发生时，Keymap 使用其映射来调用适当的处理程序。

当你创建一个 Keymap 时，你可以传递一个 JavaScript 对象来表示 Keymap 的初始绑定集。此对象的属性名称 是关键标识符，属性值是处理函数。 创建 Keymap 后，您可以通过传递一个键来添加新的绑定 bind() 方法的标识符和处理函数。您可以删除一个 通过将键标识符传递给 unbind() 方法进行绑定。

要使用 Keymap，调用它的 install() 方法，传递一个 HTML 元素， 比如文档对象。 install() 将 onkeydown 事件处理程序添加到 指定的对象。调用此处理程序时，它确定键 被按下的键的标识符并调用处理函数（如果有）， 绑定到该密钥标识符。一个 Keymap 可以安装在多个 一个 HTML 元素。

关键标识符

键标识符是键加的不区分大小写的字符串表示 同时按住的任何修饰键。键名是 通常是键上的（未移位的）文本。合法键名包括“A”、“7”、 “F2”、“PageUp”、“Left”、“Backspace”和“Esc”。

请参阅此模块中的 Keymap.keyCodeToKeyName 对象以获取名称列表。 这些是 DOM Level 3 标准定义的名称的子集，并且 该类在实现时会使用事件对象的key属性。

键标识符还可以包括修饰键前缀。这些前缀是 Alt、Ctrl、Meta 和 Shift。它们不区分大小写，必须分开 从键名和彼此之间使用空格或下划线， 连字符或 +。例如：“SHIFT+A”、“Alt_F2”、“meta-v”和“ctrl alt left”。 在 Mac 上，Meta 是 Command 键，Alt 是 Option 键。一些浏览器 将 Windows 键映射到 Meta 修饰符。

处理函数

处理程序作为文档或文档元素的方法调用 键盘映射已安装并​​传递两个参数： 1) keydown 事件的事件对象 2) 被按下的键的键标识符 处理程序返回值成为 keydown 处理程序的返回值。 如果处理函数返回 false，则键盘映射将停止冒泡并 取消与 keydown 事件关联的任何默认操作。

...

Answer 1

代码总结：

• KeyMap 的新实例是通过 new 关键字创建的。
  可选地，可以传递一个包含键映射的对象，以预先绑定：

  {
    "key-combi1": func1,   //key-combi such as alt+a, ctrl+c, shift+s
    "key-combi2": func2,
    ....
    "key-combin": funcn    //<-- Last property should not end with a comma
  }
  

• 创建新实例（var keymap = new Keymap();）后，可以使用以下方法（按逻辑时间顺序监听）：

  1. bind - 添加额外的键绑定
     keymap.bind( "key-combi", function );
  2. unbind - 删除键绑定
     keymap.unbind( "key-combi" );
  3. install - 将键映射附加到元素（绑定到 keydown 事件）
     keymap.install( element );

示例

使用此方法的最简单方法如下所示：

var keymap = new Keymap;                       // Create a new instance of Keymap
keymap.bind("ctrl_a", function(event, keyid) { // Bind key combi: ctrl+a
    alert("Key pressed down! KeyId: " + keyid)
});
keymap.install(document.body);                 // Attach keymap to <body>

另一种方法，结果相同：

var keymap = new Keymap({                      // Create a new instance of Keymap
    "ctrl_a": function(event, keyid) {         // Bind key combi: ctrl+a
        alert("Key pressed down! KeyId: " + keyid)
    }
});
keymap.install(document.body);                 // Attach keymap to <body>