Smooth scroll angular2

Question

I am having trouble getting a smooth scroll service to work in angular 2. Are there any services for smooth scrolling, or plain anchor scrolling, that might work until the angular 2 team gets the $anchorScroll angular2 equivalent working?

So far I have just tried:

Setting *ngFor loop incremental id on a parent div

[attr.id]="'point' + i"

Calling a scrollto on a button with the id passed

<button 
     type="button" 
     class="btn btn-lg btn-default " 
     (click)="smoothScroll('point'+i)">
           Scroll to point
</button>

And in the associated component I am trying to implement a plain js smooth scroll function

smoothScroll(eID) {
        var startY = currentYPosition();
        var stopY = elmYPosition(eID);
        var distance = stopY > startY ? stopY - startY : startY - stopY;
        if (distance < 100) {
            scrollTo(0, stopY); return;
        }
        var speed = Math.round(distance / 100);
        if (speed >= 20) speed = 20;
        var step = Math.round(distance / 25);
        var leapY = stopY > startY ? startY + step : startY - step;
        var timer = 0;
        if (stopY > startY) {
            for (var i = startY; i < stopY; i += step) {
                setTimeout(this.win.scrollTo(0, leapY), timer * speed);
                leapY += step; if (leapY > stopY) leapY = stopY; timer++;
            } return;
        }
        for (var i = startY; i > stopY; i -= step) {
            setTimeout(this.win.scrollTo(0,leapY), timer * speed);
            leapY -= step; if (leapY < stopY) leapY = stopY; timer++;
        }
    }
function currentYPosition() {
    // Firefox, Chrome, Opera, Safari
    if (self.pageYOffset) return self.pageYOffset;
    // Internet Explorer 6 - standards mode
    if (document.documentElement && document.documentElement.scrollTop)
        return document.documentElement.scrollTop;
    // Internet Explorer 6, 7 and 8
    if (document.body.scrollTop) return document.body.scrollTop;
    return 0;
}
function elmYPosition(eID) {
    var elm = document.getElementById(eID);
    var y = elm.offsetTop;
    var node = elm;
    while (node.offsetParent && node.offsetParent != document.body) {
        node = node.offsetParent;
        y += node.offsetTop;
    } return y;
}

I'm also trying to give access to the window for the this._win.scrollTo which is coming from a window provider service

import {Injectable, Provider} from 'angular2/core';
import {window} from 'angular2/src/facade/browser';
import {unimplemented} from 'angular2/src/facade/exceptions';

function _window(): Window {
  return window
}

export abstract class WINDOW {
  get nativeWindow(): Window {
    return unimplemented();
  }
}

class WindowRef_ extends WINDOW {
  constructor() {
    super();
  }
  get nativeWindow(): Window {
    return _window();
  }
}

export const WINDOW_PROVIDERS = [
  new Provider(WINDOW, { useClass: WindowRef_ }),
];

** EDIT ---------------------**

I changed the this.win.scrollTo to this.win.window.scrollTo and now I am getting an effect similar to angular1.x $anchorscroll where the scroll is a snappy just instead of a smooth transition, but the scroll is not smooth and I am getting the following exception error.

UPDATE

I am no longer getting that error after finding out that angular2 is doing the setTimeout a bit differently, but the scroll is still instantaneous and not a smooth scroll.

I changed

  setTimeout(this.win.scrollTo(0, leapY), timer * speed);

to

 setTimeout(() => this.win.scrollTo(0, leapY), timer * speed);

Answer 1

Thanks to the accepted answer I was able to implement a smooth "scroll to top". Scrolling to the top is actually even easier than scrolling to a particular target element since we are scrolling to the 0-position always. Here is the code:

scrollTo(yPoint: number, duration: number) {
    setTimeout(() => {
        window.scrollTo(0, yPoint)
    }, duration);
    return;
}

smoothScrollToTop() {
    let startY = this.currentYPosition();
    let stopY = 0; // window top
    let distance = stopY > startY ? stopY - startY : startY - stopY;
    if (distance < 100) {
        window.scrollTo(0, stopY);
        return;
    }
    let speed = Math.round(distance / 100);
    let step = speed;
    speed = Math.max(9, speed); //min 9 otherwise it won't look smooth
    let leapY = stopY > startY ? startY + step : startY - step;
    let timer = 0;
    if (stopY > startY) {
        for (let i = startY; i < stopY; i += step) {
            // since setTimeout is asynchronous, the for-loop will will fire all scrolls
            // nearly simoultaniously. Therefore, we need to multiply the speed with
            // a counter which lets the scrolls start with a growing offset which lets the
            // setTimeout wait for a growing time till it scrolls there
            // that way, we prevent the window to scroll instantly to the target Yposition
            this.scrollTo(leapY, timer * speed);
            leapY += step; if (leapY > stopY) leapY = stopY; timer++;
        }
        return;
    } else {
        for (let i = startY; i > stopY; i -= step) {
            this.scrollTo(leapY, timer * speed);
            leapY -= step; if (leapY < stopY) leapY = stopY; timer++;
        }
    }
}

currentYPosition() {
    // Firefox, Chrome, Opera, Safari
    if (self.pageYOffset) return self.pageYOffset;
    // Internet Explorer 6 - standards mode
    if (document.documentElement && document.documentElement.scrollTop)
        return document.documentElement.scrollTop;
    // Internet Explorer 6, 7 and 8
    if (document.body.scrollTop) return document.body.scrollTop;
    return 0;
}

If you want, you can let your "Scroll-To-Top" button appear dynamically when user scrolls:

@HostListener('window:scroll', ['$event'])
onWindowScroll(event) {
    this.onScrollFadeInOutScrollToTopButton();
}

shouldShowScrollToTop: boolean = false;

onScrollFadeInOutScrollToTopButton() {
    this.shouldShowScrollToTop = (window.pageYOffset >= window.screen.height/2);
}

And the HTML for the Scroll-to-top Button:

<div class="back-to-top">
<button *ngIf="shouldShowScrollToTop" [@fadeInOutTrigger]="animateButtonEntryState" class="mat-primary" md-fab (click)="smoothScrollToTop()">^</button>

As you can see, that button also has an animation trigger. You can think about using an icon for the button and ideally, your button should have a position:fixed; style.

Answer 2

example:

function goToElement(elemId){
 let element = window.getElementById(elemId);
 element.scrollIntoView({behavior: "smooth"});
}

Answer 3

there is a method in the window object called scrollTo(). If you set the behavior to 'smooth' the page will handle the smooth scroll. example (scroll to top of page):

 window.scrollTo({ left: 0, top: 0, behavior: 'smooth' });

And with fallback example:

    try 
    { 
     window.scrollTo({ left: 0, top: 0, behavior: 'smooth' });
     } catch (e) {
      window.scrollTo(0, 0);
      }