React-scrollable-feed-virtualized NPM

UX-wise, asking a user to scroll down manually a chat box when new messages arrive is quite painful. react-scrollable-feed aims to alleviate the burden of managing scrolling concerns from React developers. The same concept applies to any other kind of feed where new content arrives dynamically.

Virtualized version of react-scrollable-feed package.

Demo

View a live demo here.

Install

npm install --save react-scrollable-feed-virtualized

Usage

import * as React from 'react'

import ScrollableFeedVirtualized from 'react-scrollable-feed-virtualized'

class App extends React.Component {
  render() {
    const items = ['Item 1', 'Item 2'];

    return (
      <ScrollableFeedVirtualized>
        {items.map((item, i) => <div key={i}>{item}</div>)}
      </ScrollableFeedVirtualized>
    );
  }
}

Virtualized

Give style: object; prop to your item and set the styles below for the wrapper <div>:

position: "absolute",
top: style['top'],
marginTop: style['marginTop'],
width: "calc(100% - 25px)",

Options

forceScroll

Type: boolean
Default: false

If set to true, will scroll to the bottom after each update on the component. By default, if the scrollable section is not at the bottom before the update occurs, it will leave the scroll at the same position.

animateScroll

Type: (element: HTMLElement, offset: number) => void
Default:

if (element.scrollBy) {
  element.scrollBy({ top: offset });
}
else {
  element.scrollTop = offset;
}

Allows to override the scroll animation by any implementation.

onScrollComplete

Type: () => void
Default: () => {}

Is called after the scroll animation has been executed.

changeDetectionFilter

Type: (previousProps: ScrollableFeedVirtualizedComponentProps, newProps: ScrollableFeedVirtualizedComponentProps) => boolean
Default: () => true

Allows to customize when the scroll should occur. This will be called everytime a componentDidUpdate happens, which means everytime one of the props changes. You will receive as parameters the previous and the new props.

Note: ScrollableFeedVirtualizedComponentProps is defined as Readonly<{ children?: ReactNode }> & Readonly<ScrollableFeedVirtualizedProps>

If you want to compare the last children from both the previous and new props, you could do something like this :

import * as React from 'react'

import ScrollableFeedVirtualized from 'react-scrollable-feed'

class App extends React.Component {
  changeDetectionFilter(previousProps, newProps) {
    const prevChildren = previousProps.children;
    const newChildren = newProps.children;

    return prevChildren !== newChildren
      && prevChildren[prevChildren.length - 1] !== newChildren[newChildren.length - 1];
  }

  render() {
    const items = ['Item 1', 'Item 2'];

    return (
      <ScrollableFeedVirtualized
        changeDetectionFilter={this.changeDetectionFilter}
      >
        {items.map((item, i) => <div key={i}>{item}</div>)}
      </ScrollableFeedVirtualized>
    );
  }
}

export default App;

className

Type: string
Default: undefined

CSS class that can be added on the wrapping div created by ScrollableFeedVirtualized.

viewableDetectionEpsilon

Type: number
Default: 2

Indicates the number of pixels of difference between the actual bottom and the current position that can be tolerated. The default setting should be fine for most use cases.

onScroll

Type: (isAtBottom: boolean) => void
Default: () => {}

Is called when the onScroll event is triggered on the wrapper div created by ScrollableFeedVirtualized.

Provides isAtBottom boolean value as a parameter, which indicates if the scroll is at bottom position, taking viewableDetectionEpsilon into account.