How to make the width of block with position:fixed as the parent?

There are vypadalo,which should fall position:fixed; (absolute can't use for some reason) on the place where located.The problem is that it doesn't take rubber the width of the container, there may be some hacks to do this?
June 14th 19 at 20:26
1 answer
June 14th 19 at 20:28
js to set the width of the container wypadki

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