Why [removed] = launchFullscreen(document.documentElement); not work?

Question

I use launchFullscreen() function for get page full screen. It\'s work perfect with button onClick.But It doesn\'t work with window.onload

Answer 1

See the specification:

If any of the following conditions are true, queue a task to fire an event named fullscreenerror with its bubbles attribute set to true on the context object's node document, and then terminate these steps

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This algorithm is not allowed to show a pop-up.

Full screen mode may only be triggered at times when it is allowed to show a popup.

You may only show a popup in response to a user event.

A click is a user event.

The document loading is not.

There is no way around this.

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An an aside, as pointed out in Theo's answer, you are calling launchFullscreen immediately and trying to use its return value (not a function) as the load event handler. In this case, it makes no difference though.