To make animation when scrolling in pure javascript?

or using jQuery, without connecting with other libraries?
The point is that the animation should be played when scrolling, once is enough. Also the button "up": only appears in certain places of the page: for example, after scrolling the entire header (height 100%), but disappears on the CTA blocks, then when you scroll appears again?
July 9th 19 at 10:46

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