What makes the left right top and bottom to 0 for the block with absolute positioning?

There is here such code https://jsfiddle.net/api/post/library/pure/

I don't understand why left right top bottom with a value of 0 stretch absolutely positioned div with a corresponding class on the entire screen.

Please tell how it works or give a link to the article some
March 12th 20 at 07:57
2 answers
March 12th 20 at 07:59
I don't understand why
Because you say that all the angles of the child element must match the corners of the parent*.
It would be a pretty short article.

* who provided a positioning different from static.
Because you say that all the angles of the child element must match the corners of the parent*.

and those properties left right top bottom have any default values before I set manually? - bailee.Schinn commented on March 12th 20 at 08:02
@bailee.Schinn, are aligned to the top-left edge... - Jake_Murray commented on March 12th 20 at 08:05
March 12th 20 at 08:01
Just check the properties of positioning and absolute positioning, especially with top/left/right/bottom. If you set the opposite value, then they both primenantis and stretched a block. For example, top 0, bottom-50px will do the top edge of the block at level 0 relative to the "block reference", and climbs down to 50px from the same.

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