@d3fc/d3fc-data-join

A wrapper around D3's data join which simplifies some of the common problems that have been run into with our particular usage patterns, and facilitates the d3fc decorate pattern. These are not going to be universally applicable. As always it’s important to understand the abstraction and in many cases a vanilla data join may be simpler or perform better.
This blog post (Building Components with Data Join) introduces the rationale behind this component.
Main D3FC package

Installing

npm install @d3fc/d3fc-data-join

API Reference

The data-join component is a relatively lightweight wrapper around d3's selectAll/data data-join, which allows decoration of the result. This is achieved by appending the element to the enter selection before exposing it. A default transition of fade in/out is also implicitly added but can be modified.
# fc.dataJoin(element, className)
Constructs a new data-join component instance. Optionally an element or an element and a className can be specified, this is functionally equivalent to calling their methods as defined below.
# dataJoin(selection, data)
Invoke with a selection containing the parent element and the data to be joined.

import { dataJoin } from 'd3fc-data-join';
import { select } from 'd3-selection';

const join = dataJoin('li', 'animal');

join(select('ul'), ['Aardvark', 'Beaver', 'Cat'])
  .text(d => d);

The return value is a selection containing all new and existing nodes. Two additional methods are exposed for retrieving a selection containing only the new nodes (.enter()) and the removed nodes (.exit()).

import { dataJoin } from 'd3fc-data-join';
import { select } from 'd3-selection';

const join = dataJoin('li', 'animal');

const update = join(select('ul'), ['Aardvark', 'Beaver', 'Cat'])
  .text(d => d);

update.enter()
  .attr('data-', d => d);

If d3-transition is available, new nodes will have a fade-in transition applied and removed nodes will have a fade-out transition applied. The transition timings can be controlled from the container selection passed in or by explicitly setting transition.

import { dataJoin } from 'd3fc-data-join';
import { select } from 'd3-selection';
import { transition } from 'd3-transition';

const quickTransition = transition()
  .duration(300);

const join = dataJoin('li', 'animal');

const container = select('ul')
  .transition(quickTransition);

join(container, ['Aardvark', 'Beaver', 'Cat'])
  .text(d => d);

To disable transitions, explicitly retrieve the selection from the transition before passing it in -

import { dataJoin } from 'd3fc-data-join';
import { select } from 'd3-selection';
import { transition } from 'd3-transition';

const quickTransition = transition()
  .duration(300);

const join = dataJoin('li', 'animal');

const root = select('body')
  .transition(quickTransition);

const container = root.select('ul')
  .selection();

join(container, ['Aardvark', 'Beaver', 'Cat'])
  .text(d => d);

# dataJoin.element(element)
Sets the element name used to select elements and to create elements for insertion. Defaults to an SVG g element. See className for a description of the selector used.
# dataJoin.className(className)
Set the class name used to select elements and applied to inserted elements. Defaults to null. If set to null, only the element is used as the selector. If non-null, the selector provided to selectAll is -

`${element}.${className}`

# dataJoin.key(keyFunc)
Specifies the key function used by the data-join. Defaults to index-based. Equivalent to specifying a key argument when calling selection.data().
# dataJoin.transition(transition)
Specifies the transition to be used if an implicit transition is not supplied as the container. Defaults to null which disables transitions.