javascript - javascript alt键

Question

我们正在创建一个看起来像桌面窗口的 Web 用户界面。现在我们需要处理Alt密钥。按下键时Alt，焦点转到上层菜单。

在 Javascript 中，如何在按下AltONLYAlt键时获取键事件？我需要确保没有同时按下其他键。

提前致谢。

Answer 1

也许像这样

document.onkeydown = keydown;

function keydown(evt) {
    if (!evt) evt = event;
    if (evt.altKey) {
        alert('alt');
    }
} // function keydown(evt)​

Answer 2

工作演示

document.onkeyup = KeyCheck;       

function KeyCheck(e)
{
   var KeyID = (window.event) ? event.keyCode : e.keyCode;
   switch(KeyID)
   {
      case 18:
      document.Form1.KeyName.value = "Alt";
      // do your work on alt key press....
      break; 

      case 17:
      document.Form1.KeyName.value = "Ctrl";
      break;
   }
}

你的html可能是这样的

<form name="Form1">

<input type="text" name="KeyName" value="" />

</form>​

注意：如果您想在其他控件/类型上获取 alt 事件，而不是根据您的要求对其进行修改。

Answer 3

我不知道这是否是最优雅的解决方案，但效果很好。

$(function()
{
    //Flag to check if another key was pressed with alt
    var vAnotherKeyWasPressed = false;
    //ALT keycode const
    var ALT_CODE = 18;

    //When some key is pressed
    $(window).keydown(function(event)
    {
        //Identifies the key
        var vKey = event.keyCode ? event.keyCode : event.which ? event.which : event.charCode;
        //The last key pressed is alt or not? 
        vAnotherKeyWasPressed = vKey != ALT_CODE;
    });

    //When some key is left
    $(window).keyup(function(event)
    {
        //Identifies the key
        var vKey = event.keyCode ? event.keyCode : event.which ? event.which : event.charCode;

        //If the key left is ALT and no other key is pressed at the same time...
        if (!vAnotherKeyWasPressed && vKey == ALT_CODE)
        {
            //Focus the menu
            $('#myMenu').focus();
            //Stop the events for the key to avoid windows set the focus to the browser toolbar 
            return false;
        }
    });
});

Answer 4

就放e.preventDefault();

$(document).on('keydown', function (e) {
    if (e.key === 'Alt') {
        e.preventDefault();
    }
});