js键盘事件keydown事件、防止重复触发以及组合键的配合使用

// 监听键盘按下事件
  document.addEventListener('keydown', function(event) {
    // 输出按下的键的键码
    console.log('Key pressed:', event.key, 'Key code:', event.keyCode);
  });

let keyDownFlag = false;

  // 监听键盘按下事件
  document.addEventListener('keydown', function(event) {
    if (!keyDownFlag) {
      keyDownFlag = true;
      console.log('Key pressed:', event.key, 'Key code:', event.keyCode);
    }
  });

  // 监听键盘释放事件
  document.addEventListener('keyup', function() {
    keyDownFlag = false;
  });

// 监听键盘按下事件
  document.addEventListener('keydown', function(event) {
    if (!event.repeat) {
      console.log('Key pressed:', event.key, 'Key code:', event.keyCode);
    }

document.onkeydown = function (oEvent) {
    console.log(oEvent);
}

document.onkeydown = functionb(oEvent) {
  var oEvent = oEvent || window.oEvent; 
  //获取键盘的keyCode值
  var nKeyCode = oEvent.keyCode || oEvent.which || oEvent.charCode;
  //获取ctrl 键对应的事件属性
  var bCtrlKeyCode = oEvent.ctrlKey || oEvent.metaKey;
   if( oEvent.nKeyCode == 83 && bCtrlKeyCode  ) {
      alert('save');
       //doSomeThing...
   }
}

document.onkeydown = functionb(e) {
	if(e.altKey && e.keyCode == 81){
	      if(e.repeat){
	        return 
	      }
	      //todo somethink
    }
}

console.log(ev.ctrlKey);
console.log(ev.shiftKey);
console.log(ev.altKey);