How to know if a Xul window is minimized?

Xul's window.sizemode documentation says:

When a window is minimized, the sizemode attribute is not updated. This is done so th开发者_运维百科at if a window is closed while minimized, its persisted sizemode attribute wouldn't be minimized.

so, is there a way to know when it's minimized?

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The documentation you pointed said:

To get the window state from JavaScript code, use window.windowState.

The window.windowState link is broken. But I could find its documentation. It says you can check if the attribute windowState is equals to the constant STATE_MINIMIZED.