Reactjs: How can access property of scrollbox (hor

Question

I have a scroll view in this fashion: a succession of views wrapped horizontally on a container.

      <div id="scroller"  ref="scroller" onClick=
{this.onClick.bind(this)} onMouseMove={this._onMouseMove.bind(this)}>
                {this.state.pma.map((Item, index) => (
                  <this.state.typePma
                    key           = {index}
                    pma           = {Item}
                    onDateChange  = {(child)  => this.onDateChange(child)}
                    redisplay     = {()       => this.redisplay()}
                    />
                  ))}
              </div>

I'd like to know how I can get the horizontal offset of the scrollview and manipulate it programmatically: I'd like to move my scrollview with simple drag with the mouse. For the moment, the behavior is that I need to drag the horizontal slidebar but that don't work if I try the same on the view.

Answer 1

I am really not sure what you are looking for, but if you are looking for a way to control the scroll behavior for lazy loading in your app, so for e.g, if the user reach the bottom of the scroll you want to load more data, you can do it like this.

class ScrollablePage extends Component {

  componentDidMount() {
    // Add Scroll Event After The UI Has Been rendered
    window.addEventListener("scroll", this.onHandleScrollEvent);
  }

  onHandleScrollEvent = () => {   
    const el = document.body;
    /*
     * el.scrollTop => This tells us how much a user has scrolled from up
     * Math.ceil(el.scrollTop) => returns value in whole rather then float
     */

    // this will start paginating when there is a difference of 100px from bottom
    const bottomSpace = 100; 
    const bottomReachLimit = Math.ceil(el.scrollTop) + (bottomSpace); 
    if (el.scrollHeight - el.clientHeight <= bottomReachLimit) {
        // console.log('Bottom reached, starting pagination');
        // Do your magic here when reached bottom
    } else { 
       // console.log('Bottom not reached');
    }
  }

  render () {
     return (
       <div>
         {/* YOUR SCROLLABLE CONTENT HERE */}
       </div>
     );
  }

}

But if you want to control the Scroll behavior through code you can do something like this. The code written below will scroll to the bottom of the page on componentDidMount() but this gives you an idea how you can control the scroll behavior in an imperative way.

 import React, { Component } from 'react';
 import { findDOMNode } from "react-dom";

 class ScrollablePage extends Component {
    componentDidUpdate() {
      this.scrollToBottom();
    }

    scrollToBottom() {
       const el = findDOMNode(this)
       const scrollHeight = el.scrollHeight;
       const totalContainerHeight = el.clientHeight;
       const shouldScroll = scrollHeight - totalContainerHeight;

       const myInterval = setInterval(() => {
         if (shouldScroll > 0) {
           el.scrollTop = el.scrollTop + 70;
           if (el.scrollTop + el.clientHeight >= el.scrollHeight - 30) {
             clearInterval(myInterval);
           }
         }
       }, 20);
    }

    render () {
      return (
        <div>
           {/* YOUR SCROLLABLE CONTENT HERE */}
        </div>
      );
    }
 }