Created
February 19, 2020 21:45
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Scroll arrow hides on scroll (optimized for passive listeners)
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| //scroll arrow hides on scroll | |
| function hideOnScroll() { | |
| var scroll_el = document.getElementById('scroll'); | |
| if ( document.getElementById('app').scrollTop > 20 ) { | |
| scroll_el.style.display = "none"; | |
| } else { | |
| scroll_el.style.display = "block"; | |
| } | |
| } | |
| var supportsPassive = false; | |
| try { | |
| var opts = Object.defineProperty({}, 'passive', { | |
| get: function() { | |
| supportsPassive = true; | |
| } | |
| }); | |
| window.addEventListener("testPassive", null, opts); | |
| window.removeEventListener("testPassive", null, opts); | |
| } catch (e) {} | |
| if (document.getElementById('scroll')) { | |
| document.getElementById('app').addEventListener('scroll', hideOnScroll, supportsPassive ? { passive: true } : false); | |
| } |
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