BookStack Code Mirror - bookstack/blob - resources/js/components/back-to-top.js

   1 import {Component} from './component';
   2
   3 export class BackToTop extends Component {
   4
   5     setup() {
   6         this.button = this.$el;
   7         this.targetElem = document.getElementById('header');
   8         this.showing = false;
   9         this.breakPoint = 1200;
  10
  11         if (document.body.classList.contains('flexbox')) {
  12             this.button.style.display = 'none';
  13             return;
  14         }
  15
  16         this.button.addEventListener('click', this.scrollToTop.bind(this));
  17         window.addEventListener('scroll', this.onPageScroll.bind(this));
  18     }
  19
  20     onPageScroll() {
  21         const scrollTopPos = document.documentElement.scrollTop || document.body.scrollTop || 0;
  22         if (!this.showing && scrollTopPos > this.breakPoint) {
  23             this.button.style.display = 'block';
  24             this.showing = true;
  25             setTimeout(() => {
  26                 this.button.style.opacity = 0.4;
  27             }, 1);
  28         } else if (this.showing && scrollTopPos < this.breakPoint) {
  29             this.button.style.opacity = 0;
  30             this.showing = false;
  31             setTimeout(() => {
  32                 this.button.style.display = 'none';
  33             }, 500);
  34         }
  35     }
  36
  37     scrollToTop() {
  38         const targetTop = this.targetElem.getBoundingClientRect().top;
  39         const scrollElem = document.documentElement.scrollTop ? document.documentElement : document.body;
  40         const duration = 300;
  41         const start = Date.now();
  42         const scrollStart = this.targetElem.getBoundingClientRect().top;
  43
  44         function setPos() {
  45             const percentComplete = (1 - ((Date.now() - start) / duration));
  46             const target = Math.abs(percentComplete * scrollStart);
  47             if (percentComplete > 0) {
  48                 scrollElem.scrollTop = target;
  49                 requestAnimationFrame(setPos.bind(this));
  50             } else {
  51                 scrollElem.scrollTop = targetTop;
  52             }
  53         }
  54
  55         requestAnimationFrame(setPos.bind(this));
  56     }
  57
  58 }