如何在 angular 中单击按钮将列表滚动到顶部？

Question

could you please tell me how to scroll the list to top on button click in angular? I tried like this

 scrollToTop(el){
    el.scrollIntoView();
  }

  <button (click)="scrollToTop(target)">scroll to top</button>

It scroll the list to top.but it hide my addressbar and then user not able see header I think it is not a good solution.anybody have any other good solution

here is my code https://stackblitz.com/edit/angular-f9qxqh?file=src%2Fapp%2Fapp.component.html

Answer 1

You can scroll to the top of the list by setting the scrollTop property of the container to zero. See this stackblitz for a demo.

<div #container class="container">
  <ul>
    <li *ngFor="let i of items">{{i}}</li>
  </ul>
</div>

<button (click)="container.scrollTop = 0">scroll to top</button>

---

Here is a simple method that scrolls smoothly to the top of the list. It is based on this answer by bryan60 , and adapted to RxJS 6. You can try it in this stackblitz .

<button (click)="scrollToTop(container)">scroll to top</button>

import { interval as observableInterval } from "rxjs";
import { takeWhile, scan, tap } from "rxjs/operators";
...

scrollToTop(el) {
  const duration = 600;
  const interval = 5;
  const move = el.scrollTop * interval / duration;
  observableInterval(interval).pipe(
    scan((acc, curr) => acc - move, el.scrollTop),
    tap(position => el.scrollTop = position),
    takeWhile(val => val > 0)).subscribe();
}

Answer 2

You add the scroll to your container, so it works on container not on ul

app.component.html

<div class="container" #container>
  <ul #target>
    <li *ngFor="let i of items">{{i}}</li>
  </ul>
</div>
<button (click)="scrollToTop(container)">scroll to top</button>

app.component.ts

scrollToTop(el) {
 el.scrollTop = 0;          
}

For smooth scrolling , use this :

scrollToTop(el) {
    var to = 0;
    var duration = 1000;
    var start = el.scrollTop,
        change = to - start,
        currentTime = 0,
        increment = 20;

    var easeInOutQuad = function(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;
    }

    var animateScroll = function() {        
        currentTime += increment;
        var val = easeInOutQuad(currentTime, start, change, duration);

        el.scrollTop = val;
        if(currentTime < duration) {
            setTimeout(animateScroll, increment);
        }
    }
    animateScroll();    
}

Answer 3

Typescript

ngOnInit(): void {

const scroller = document.querySelector(".wrapper");
scroller?.addEventListener("scroll", (event) => {
  if(scroller?.scrollTop > 300){
    this.windowScrolled = true;
  } else{
    this.windowScrolled = false;
  }
}); 
}



scrollToTop(): void {
    document.getElementsByClassName('wrapper')[0].scrollTo(0,0);
  }

HTML

<p>
<a *ngIf="windowScrolled" class="topButton" (click)="scrollToTop()" title="Go to top">
  <i class="pi pi-angle-double-up"><i class="pi pi-angle-double-up"></i></i>
</a>

SCSS

.topButton{
    position: fixed;
    transition: all 0.2s ease-in-out;
    z-index: 1030;
    right: 30px;
    bottom: 50px;
    font-weight: bolder;
    cursor: pointer;
    background-color: #002266;
    color: white;
    width: 23px;
    height: 34px;
    text-align: center;
    vertical-align: middle;
    border-radius: 15px;
    padding: 3px;
}