joshyu / incremental-dom

Incremental DOM

Overview

Incremental DOM is a library for building up DOM trees and updating them in-place when data changes. It differs from the established virtual DOM approach in that no intermediate tree is created (the existing tree is mutated in-place). This approach significantly reduces memory allocation and GC thrashing for incremental updates to the DOM tree therefore increasing performance significantly in some cases.

Incremental DOM is primarily intended as a compilation target for templating languages. It could be used to implement a higher level API for human consumption. The API was carefully designed to minimize heap allocations and where unavoidable ensure that as many objects as possible can be de-allocated by incremental GC. One unique feature of its API is that it separates opening and closing of tags so that it is suitable as a compilation target for templating languages that allow (temporarily) unbalanced HTML in templates (e.g. tags that are opened and closed in separate templates) and arbitrary logic for creating HTML attributes. Think of it as ASM.dom.

Usage

HTML is expressed in Incremental DOM using the elementOpen, elementClose, elementVoid and text methods. Consider the following example:

var IncrementalDOM = require('incremental-dom'),
    elementOpen = IncrementalDOM.elementOpen,
    elementClose = IncrementalDOM.elementClose,
    elementVoid = IncrementalDOM.elementVoid,
    text = IncrementalDOM.text;

function render(data) {
  elementVoid('input', '', [ 'type', 'text' ]);
  elementOpen('div', '', null);
    if (data.someCondition) {
      text(data.text);
    }
  elementClose('div');
}

To render or update an existing DOM node, the patch function is used:

var patch = require('incremental-dom').patch;

var data = {
  text: 'Hello World!',
  someCondition: true
};

patch(myElement, function() {
  render(data);
});

data.text = 'Hello World!';

patch(myElement, function() {
  render(data);
});

Templating Languages

We are building a new JavaScript backend for the Closure Templates templating language. Follow along on Github.

If you work on a templating language we'd love to see Incremental DOM adopted as an alternative backend for it. This isn’t easy, we are still working on ours and will for a while, but we're super happy to help with it.

Here's an example.

Docs

• Introducing Incremental Dom
• Docs and demos

Installation

npm install incremental-dom

Development

To install the required development packages, run the following command:

npm i

Running tests

To run once:

gulp unit

To run on change:

gulp unit-watch

Building

To build once:

gulp js

To build on change:

gulp js-watch