Diffing the DOM without virtual DOM
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Andrea Giammarchi
Andrea Giammarchi 2.0.3
Latest commit a66d5dd Jan 17, 2019

README.md

domdiff

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A vDOM-less implementation of the petit-dom diffing logic, at the core of hyperHTML.

V2 breaking change

  • the good old snabdom diff logic has been 100% replaced
  • lists with null or undefined nodes are not allowed anymore

... but I guess having null nodes in the equation was quite possibly a bad idea in the first place ...

V2 Diffing Strategies:

  • common prefixes
  • common suffixes
  • skip same lists
  • add boundaries
  • remove boundaries
  • simple sub-sequences insertions and removals
  • one to many and many to one replacements
  • fast inverted list swap
  • O(ND) algo with a limit of 50 attempts
  • last fallback with a simplified Hunt Szymanski algorithm

The current goal is to have in about 1K the best DOM diffing library out there.

V1 breaking change

The signature has moved from parent, current[], future[], getNode(), beforeNode to parent, current[], future[], {before, compare(), node()}.

Signature

futureNodes = domdiff(
  parentNode,     // where changes happen
  currentNodes,   // Array of current items/nodes
  futureNodes,    // Array of future items/nodes (returned)
  options         // optional object with one of the following properties
                  //  before: domNode
                  //  compare(generic, generic) => true if same generic
                  //  node(generic) => Node
);

How to import it:

  • via CDN, as global variable: https://unpkg.com/domdiff
  • via ESM, as external module: https://unpkg.com/domdiff/esm/index.js
  • via CJS: const EventTarget = require('domdiff').default; ( or require('domdiff/cjs').default )
  • via bundlers/transpilers: import domdiff from 'domdiff'; ( or from 'domdiff/esm' )

Example

var nodes = {
  a: document.createTextNode('a'),
  b: document.createTextNode('b'),
  c: document.createTextNode('c')
};

var parentNode = document.createElement('p');
var childNodes = [nodes.a, nodes.c];
parentNode.append(...childNodes);
parentNode.textContent;
// "ac"

childNodes = domdiff(
  parentNode,
  childNodes,
  [nodes.a, nodes.b, nodes.c]
);

parentNode.textContent;
// "abc"

Compatibility:

Every. JavaScript. Engine.

A {node: (generic, info) => node} callback for complex data

The optional {node: (generic, info) => node} is invoked per each operation on the DOM.

This can be useful to represent node through wrappers, whenever that is needed.

The passed info value can be:

  • 1 when the item/node is being appended
  • 0 when the item/node is being used as insert before reference
  • -0 when the item/node is being used as insert after reference
  • -1 when the item/node is being removed

Example

function node(item, i) {
  // case removal or case after
  if ((1 / i) < 0) {
    // case removal
    if (i) {
      // if the item has more than a node
      // remove all other nodes at once
      if (item.length > 1) {
        const range = document.createRange();
        range.setStartBefore(item[1]);
        range.setEndAfter(item[item.length - 1]);
        range.deleteContents();
      }
      // return the first node to be removed
      return item[0];
    }
    // case after
    else {
      return item[item.length - 1];
    }
  }
  // case insert
  else if (i) {
    const fragment = document.createDocumentFragment();
    fragment.append(...item);
    return fragment;
  }
  // case before
  else {
    return item[0];
  }
}

const and = [document.createTextNode(' & ')];

const Bob = [
  document.createTextNode('B'),
  document.createTextNode('o'),
  document.createTextNode('b')
];

const Lucy = [
  document.createTextNode('L'),
  document.createTextNode('u'),
  document.createTextNode('c'),
  document.createTextNode('y')
];

// clean the body for demo purpose
document.body.textContent = '';
let content = domdiff(
  document.body,
  [],
  [Bob, and, Lucy],
  {node}
);

// ... later on ...
content = domdiff(
  document.body,
  content,
  [Lucy, and, Bob],
  {node}
);

// clean up
domdiff(
  document.body,
  content,
  [],
  {node}
);