Javascript 按键代码 "+1 enter"和 "-1 enter"

Question

有人知道如何在Javascript中检测按键代码“+1 Enter”和“-1 Enter”吗？我想检测何时一一按下键码而不是一次按下键码。

但是当我编写以下代码时，没有给出任何效果。

// +1 enter
$(document).keydown(function(e) {
    if (e.keyCode == 107 && e.keyCode == 49 && e.keyCode == 13) {
    window.alert("+1");
    }
});

// -1 enter
$(document).keydown(function(e) {
    if (e.keyCode == 109 && e.keyCode == 49 && e.keyCode == 13) {
    window.alert("-1");
    }
});

请提供专业意见。

Answer 1

为了实现这一点，您需要能够跟踪以前按下的键。请尝试以下操作:

// These are just used to display the result in the DOM--you can delete this
var $keyCodes = document.getElementById('key-codes');
var $result = document.getElementById('result');

// Used to keep track of your key presses
var trackKeyCodes = (function() {
  // Keep a private array of key codes to track
  var keyCodes = [];
  // This is the actual function that gets stored in trackKeyCodes
  return function(keyCode) {
    // Only store the last 3 key codes
    if (keyCodes.length === 3) keyCodes.splice(0, 1);
    // Add the next key code
    keyCodes.push(keyCode);
    // This just displays it in the DOM for you to see--you can delete this
    $keyCodes.innerHTML = keyCodes.join(', ');
    return keyCodes;
  };
})();
// Used to actually check the key presses
var checkKeyCodes = function(keyCodes, first, second, third) {
  return keyCodes[0] === first && keyCodes[1] === second && keyCodes[2] === third;
};

// +1 enter
$(document).keydown(function(e) {
  var keyCodes = trackKeyCodes(e.keyCode);
  if (checkKeyCodes(keyCodes, 107, 49, 13)) {
      $result.innerHTML = '+ 1';
  } else if (checkKeyCodes(keyCodes, 109, 49, 13)) {
      $result.innerHTML = '- 1';
  } else {
      $result.innerHTML = '';
  }
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p>
KeyCodes: <span id="key-codes">-</span>
</p>
<p>
Result: <span id="result">-</span>
</p>