如何在javascript中获取组合键的键码？

Question

    $(document).keydown(function(event) {

        doSomething(event);
        event.preventDefault();
    });

有了上面的代码，我就可以得到单键的键码。但是，当我使用组合键时，我得到了第一个和第二个键的事件。例如，!(Shift + 1)、$(Shift + 4)。

如何获取组合键的键码？

Answer 1

下面是一些可以帮助你的插件：

1. https://github.com/jeresig/jquery.hotkeys
2. https://github.com/madrobby/keymaster (这个是deps免费的)

Answer 2

您可以使用一个函数来扩展jquery的fn对象，该函数基于按下的键和正则表达式匹配来处理回调函数的触发

我写过一个类似的Answer，之前支持单键的正则表达式匹配，我只是稍微修改了一下，以支持多键。

  $.fn.selectedKey = (function () {
      var keys = "";
      var last = "";
      var key = "";
      return function (cb, data) {
          def.call(data, {
              ctrlKey: 2, //0: musn't be pressed, 1: must be pressed, 2: both.
              altKey: 2, // "
              invert: 0, //inverts the filter
              filter: /.*/, // A Regular Expression, or a String with a Regular Expression
              preventDefault: false //Set to true to prevent Default.
          }); //Sets the default Data for the values used,

          function validate(e) {

              var exp = new RegExp(e.data.filter.replace(/\\\\(\d)/g, String.fromCharCode("$1"))); //Creates a new RegExp from a String to e.g. allow "\2" to match the keyCode 2
              var c = !! (e.data.ctrlKey ^ e.ctrlKey ^ 1 > 0); //c == true if the above stated conditions are met e.g Ctrl Key Pressed and `ctrlKey == 1` -> true
              var a = !! (e.data.altKey ^ e.altKey ^ 1 > 0); //e.g Alt Key Pressed and `altKey == 0` -> false
              //console.log(keys,exp,c,a)
              return (exp.test(keys) && (c && a)); //Returns the validation Result
          }

          function def(obj) { //a minimal helper for default values
              for (var prop in obj) {
                  this[prop] = this[prop] || obj[prop];
              }
          }
          this.keypress(data, function (e) {

              key = e.char = String.fromCharCode(e.keyCode || e.which); //Converts the pressed key to a String
              keys += ( !! ~ (keys.indexOf(key))) ? "" : key;
              key = key["to" + (e.shiftKey ? "Upper" : "Lower") + "Case"]();
              keys = keys["to" + (e.shiftKey ? "Upper" : "Lower") + "Case"](); //case handling
              if (e.data.preventDefault) e.preventDefault();

              if ((validate(e) != e.data.invert) && keys != last) {

                  cb(e);
                  last = keys;
                  //Calls the callback function if the conditions are met
              }
          });
          if (!this.data("keyupBound")) {
              this.keyup(data, function (e) {

                  key = e.char = String.fromCharCode(e.keyCode || e.which); //Converts 
                  var t = keys.toLowerCase()
                      .split("");
                  t.splice(t.indexOf(e.char), 1);
                  keys = t.join("");
                  last = keys;
              });
              this.data("keyupBound", true);
          }
      };

  })();


$("body").selectedKey(function (e) {
    console.log("All lower characters, Numbers and 'A': " + e.char);
}, {
    filter: "^[a-z]|[0-9]|A$",
    ctrlKey: 2,
    altKey: 2
});

$("body").selectedKey(function (e) {
    console.log("KeyCode 2 " + e.char); // Ctrl + b
}, {
    filter: "\\2",
    ctrlKey: 1,
    altKey: 2
});

例如，你也可以做filter:/.{4,5}/，它可以同时按下任何4到5个键

例如，当按下A+S+D时会触发此操作

$("body").selectedKey(function (e) {
    console.log("ASD has been pressed"); // Ctrl + b
}, {
    filter: "^ASD$",
    ctrlKey: 2,
    altKey: 2
});

下面是一个关于JSBin的工作示例

编辑备注。修复了验证结果为true时按键连续触发的问题

Edit2:修复了last变量，未正确使用...

Answer 3

你需要记住哪个键被按下了。您应该监听keyup + keydown事件：

var keyCodesPressed = {};

$(document).keydown(function(event) {
  keyCodesPressed[event.which] = true;
  // here you should have all keys which are currently pressed:
  for (keyCode in keyCodesPressed) {
    // and you can loop over them and detect which are the ones currently pressed
  } 
});

$(document).keyup(function(event) {
  delete keyCodesPressed[event.which];
});