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February 15, 2019 07:07
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Automatically make all anchors to an ID'ed in-page element to smooth-scroll
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| // Automatically make all anchors to an ID'ed in-page element to smooth-scroll | |
| window.addEventListener('load', function(event) { | |
| var anchors = document.getElementsByTagName("a"); | |
| for (var i = 0, max = anchors.length; i < max; i++) { | |
| var anchor = anchors[i]; | |
| console.log(anchor); | |
| var href = anchor.getAttribute("href"); | |
| if (!href.startsWith("#")) { | |
| continue; | |
| } | |
| anchor.addEventListener("click", function(e) { | |
| e.preventDefault(); | |
| var href = this.getAttribute("href"); | |
| var name = href.substring(1); | |
| var target = document.getElementById(name); | |
| if (!target) { | |
| target = document.getElementsByTagName("body")[0]; | |
| } | |
| if (!target) { | |
| return; | |
| } | |
| var targetTop = target.getBoundingClientRect().top; | |
| console.log(target, targetTop); | |
| var currentTop = document.documentElement.scrollTop; | |
| var diff = Math.abs(targetTop - currentTop); | |
| scrollToElem(target, 100 + diff /4); | |
| }); | |
| } | |
| }); | |
| // based on https://gist.github.com/andjosh/6764939 | |
| function scrollToElem(target, duration) { | |
| var start = window.pageYOffset; | |
| var to = target.getBoundingClientRect().top; | |
| var change = to - start; | |
| var currentTime = 0; | |
| var increment = 20; | |
| function animateScroll(){ | |
| currentTime += increment; | |
| var val = easeInOutQuad(currentTime, start, change, duration); | |
| window.scrollTo(window.pageXOffset, val); | |
| if (currentTime < duration) { | |
| setTimeout(animateScroll, increment); | |
| } | |
| }; | |
| animateScroll(); | |
| //t = current time | |
| //b = start value | |
| //c = change in value | |
| //d = duration | |
| function easeInOutQuad(t, b, c, d) { | |
| t /= d/2; | |
| if (t < 1) return c/2*t*t + b; | |
| t--; | |
| return -c/2 * (t*(t-2) - 1) + b; | |
| }; | |
| } |
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