j查询键盘事件处理程序按住

Question

我想为游戏创建一个简单的事件处理程序，这是我的代码

     $(document).keydown(function(e){
      switch(e.keyCode){
        case 65: //left (a)
          console.log('left');
          break;
        case 68: //right (d)
          console.log('right');
          break;
      }
    });

问题是，如果我按住一个键，它会在一点点之后触发多次。如何防止此行为？我正在谷歌浏览器上运行我的代码

Answer 1

这是

关键重复。如果你愿意，你可以打败它，记住你已经知道密钥已关闭：

// A map to remember in
var keysdown = {};
// keydown handler
$(document).keydown(function(e){
  // Do we already know it's down?
  if (keysdown[e.keyCode]) {
      // Ignore it
      return;
  }
  // Remember it's down
  keysdown[e.keyCode] = true;
  // Do our thing
  switch(e.keyCode){
    case 65: //left (a)
      console.log('left');
      break;
    case 68: //right (d)
      console.log('right');
      break;
  }
});
// keyup handler
$(document).keyup(function(e){
  // Remove this key from the map
  delete keysdown[e.keyCode];
});

---

旁注：我认为当你使用jQuery时，e.which是更可靠的属性，因为它是由jQuery为你规范化的。

Answer 2

var keyPressed = false;
$(document).on('keydown', function(e) {
  var key;
  if (keyPressed === false) {
    keyPressed = true;
    key = String.fromCharCode(e.keyCode);
    //this is where you map your key
    if (key === 'X') {
      console.log(key);
      //or some other code
    }
  }
  $(this).on('keyup', function() {
    if (keyPressed === true) {
      keyPressed = false;
      console.log('Key no longer held down');
      //or some other code
    }
  });
});