pull-scroll

pull-stream to a infinite scrolling web pane.

streams are for programatically dealing with data that arrives or is processed over time. Many applications also have features they call "streams", or views that may contain a large number of items, if you just keep scrolling down?

pull-scroll is the simplest way to join these concepts, you can take a pull-stream of content, attach it to a scrolling element, and the scroller sets the back pressure.

when the element is filled, back pressure kicks in, and when you scroll to the end, it is released, and more data flows in.

pull-scroll can be used for both double and single ended content streams.

example

var Scroller = require('pull-scroll')
var pull = require('pull-stream')
var h = require('hyperscript')
 
var content = h('div')
var scroller = h('div', {
    style: {
      //must set overflow-y to scroll for this to work.
      'overflow-y': 'scroll',
      //and cause this element to not stretch.
      //this can also be achived using flexbox column.
      position: 'fixed', bottom:'0px', top: '0px',
      width: '600px'
    }
  }, content)
 
  //provide a render function that returns an html element.
  function render (n) {
    return h('h1', n.toString())
  }
 
  pull(
    pull.infinite(),
    Scroller(scroller, content, render)
  )
 
document.body.appendChild(scroller)

you can have attach two Scrollers to an element, one for scrolling up and one for scrolling down. (thus, a two way infinite scroller)

see example here

api

Scroller(scrollable, container, render, isPrepend, isSticky, cb) => Sink

Create a pull-stream sink where the back pressure is controlled by the scrolling of the element. scrollable needs to be an element which can scroll, and container is an optional child (otherwise elements will be added directly to scrollable)

render is a function that takes stream items and returns an html element.

If isPrepend is true, elements will be added before the first child of container, if it is false, they will be appended.

If isSticky is true, scrollable will be scrolled into position after adding an element. this will make more elements come automatically, untill you scroll away. If isSticky is false, new elements will extend the container, but not be scrolled into positon, this means the scroll will only be adjusted as the user scrolls.

If the user is scrolling to read old data (i.e. scrolling down on twitter, or up in the terminal) then use isSticky=false. If the user is scrolled to the end to get new data, (i.e. scrolling to the top on twitter, or the bottom in the terminal) then use isSticky=true.

cb is an optional callback used only for error handling. This defaults to

function (err) { if(err) console.error(err) }

License

MIT