函数：

ui.Button(label, onClick, disabled, style)

A clickable button with a text label.

Arguments:

label (String, optional):

The button's label. Defaults to an empty string.

onClick (Function, optional):

A callback fired when the button is clicked. The callback is passed the button widget.

disabled (Boolean, optional):

Whether the button is disabled. Defaults to false.

style (Object, optional):

An object of allowed CSS styles with their values to be set for this widget. Defaults to an empty object.

Returns: ui.