53 lines
No EOL
1.7 KiB
JavaScript
53 lines
No EOL
1.7 KiB
JavaScript
|
|
class BackToTop {
|
|
|
|
constructor(elem) {
|
|
this.elem = elem;
|
|
this.targetElem = document.getElementById('header');
|
|
this.showing = false;
|
|
this.breakPoint = 1200;
|
|
this.elem.addEventListener('click', this.scrollToTop.bind(this));
|
|
window.addEventListener('scroll', this.onPageScroll.bind(this));
|
|
}
|
|
|
|
onPageScroll() {
|
|
let scrollTopPos = document.documentElement.scrollTop || document.body.scrollTop || 0;
|
|
if (!this.showing && scrollTopPos > this.breakPoint) {
|
|
this.elem.style.display = 'block';
|
|
this.showing = true;
|
|
setTimeout(() => {
|
|
this.elem.style.opacity = 0.4;
|
|
}, 1);
|
|
} else if (this.showing && scrollTopPos < this.breakPoint) {
|
|
this.elem.style.opacity = 0;
|
|
this.showing = false;
|
|
setTimeout(() => {
|
|
this.elem.style.display = 'none';
|
|
}, 500);
|
|
}
|
|
}
|
|
|
|
scrollToTop() {
|
|
let targetTop = this.targetElem.getBoundingClientRect().top;
|
|
let scrollElem = document.documentElement.scrollTop ? document.documentElement : document.body;
|
|
let duration = 300;
|
|
let start = Date.now();
|
|
let scrollStart = this.targetElem.getBoundingClientRect().top;
|
|
|
|
function setPos() {
|
|
let percentComplete = (1-((Date.now() - start) / duration));
|
|
let target = Math.abs(percentComplete * scrollStart);
|
|
if (percentComplete > 0) {
|
|
scrollElem.scrollTop = target;
|
|
requestAnimationFrame(setPos.bind(this));
|
|
} else {
|
|
scrollElem.scrollTop = targetTop;
|
|
}
|
|
}
|
|
|
|
requestAnimationFrame(setPos.bind(this));
|
|
}
|
|
|
|
}
|
|
|
|
module.exports = BackToTop; |