Question

我使用以下代码从Javascript获取keycode值

   var whichCode = (window.event) ? e.which : e.keyCode;

但是，除了IE 9之外它工作正常。它在e.which上返回undefined。

Answer 1

KeyboardEvent.which从未在Internet Explorer中实现过，在其他版本中被视为已弃用。

MDN解释how to most correctly handle keyboard events：

window.addEventListener("keydown", function (event) {
  if (event.defaultPrevented) {
    return; // Should do nothing if the default action has been cancelled
  }

  var handled = false;
  if (event.key !== undefined) {
    // Handle the event with KeyboardEvent.key and set handled true.
  } else if (event.keyIdentifier !== undefined) {
    // Handle the event with KeyboardEvent.keyIdentifier and set handled true.
  } else if (event.keyCode !== undefined) {
    // Handle the event with KeyboardEvent.keyCode and set handled true.
  }

  if (handled) {
    // Suppress "double action" if event handled
    event.preventDefault();
  }
}, true);

现在，假设您没有处理keyDown事件，您也可以使用

var whichCode = e.charCode !== undefined ? e.charCode : e.keyCode;

请注意，浏览器兼容性为exactly how it is done in jQuery：

if ( event.which == null ) {
    event.which = original.charCode != null ? original.charCode : original.keyCode;
}

Answer 2

此代码在哪里执行？请添加完整的代码。你应该在事件处理程序中使用它！假设它正确放置，请尝试此

var keycodeValue = e.which || e.keyCode;

其中e是收到的事件

e.which在IE 9中不起作用

2 个答案: