mirror of
https://codeberg.org/yeentown/barkey
synced 2024-12-05 03:17:26 +00:00
50 lines
1.8 KiB
TypeScript
50 lines
1.8 KiB
TypeScript
export class StickySidebar {
|
|
private lastScrollTop = 0;
|
|
private container: HTMLElement;
|
|
private el: HTMLElement;
|
|
private spacer: HTMLElement;
|
|
private marginTop: number;
|
|
private isTop = false;
|
|
private isBottom = false;
|
|
private offsetTop: number;
|
|
private globalHeaderHeight = 59;
|
|
|
|
constructor(container: StickySidebar['container'], marginTop = 0, globalHeaderHeight = 0) {
|
|
this.container = container;
|
|
this.el = this.container.children[0] as HTMLElement;
|
|
this.el.style.position = 'sticky';
|
|
this.spacer = document.createElement('div');
|
|
this.container.prepend(this.spacer);
|
|
this.marginTop = marginTop;
|
|
this.offsetTop = this.container.getBoundingClientRect().top;
|
|
this.globalHeaderHeight = globalHeaderHeight;
|
|
}
|
|
|
|
public calc(scrollTop: number) {
|
|
if (scrollTop > this.lastScrollTop) { // downscroll
|
|
const overflow = Math.max(0, this.globalHeaderHeight + (this.el.clientHeight + this.marginTop) - window.innerHeight);
|
|
this.el.style.bottom = null;
|
|
this.el.style.top = `${-overflow + this.marginTop + this.globalHeaderHeight}px`;
|
|
|
|
this.isBottom = (scrollTop + window.innerHeight) >= (this.el.offsetTop + this.el.clientHeight);
|
|
|
|
if (this.isTop) {
|
|
this.isTop = false;
|
|
this.spacer.style.marginTop = `${Math.max(0, this.globalHeaderHeight + this.lastScrollTop + this.marginTop - this.offsetTop)}px`;
|
|
}
|
|
} else { // upscroll
|
|
const overflow = this.globalHeaderHeight + (this.el.clientHeight + this.marginTop) - window.innerHeight;
|
|
this.el.style.top = null;
|
|
this.el.style.bottom = `${-overflow}px`;
|
|
|
|
this.isTop = scrollTop + this.marginTop + this.globalHeaderHeight <= this.el.offsetTop;
|
|
|
|
if (this.isBottom) {
|
|
this.isBottom = false;
|
|
this.spacer.style.marginTop = `${this.globalHeaderHeight + this.lastScrollTop + this.marginTop - this.offsetTop - overflow}px`;
|
|
}
|
|
}
|
|
|
|
this.lastScrollTop = scrollTop <= 0 ? 0 : scrollTop;
|
|
}
|
|
}
|