Visible

visible绑定到DOM元素上，使得该元素的hidden或visible状态取决于绑定的值。如下实例：

<div data-bind="visible: shouldShowMessage">
  You will see this message only when "shouldShowMessage" holds a true value.
</div>

var viewModel = {
     shouldShowMessage: ko.observable(true) // Message initially visible
};
viewModel.shouldShowMessage(false); //隐藏元素
viewModel.shouldShowMessage(true);  //显示元素