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Miks Collaborative Editor

中文 | English

A collaborative editor that supports authorship display, image placeholder and CJK characters composition based on Quill and ShareDB.


Operational transformation (OT)

The document is represented by a collection of operations: insert, delete and retain. Each modification of the document can also be represented by a serials of OT operations. By doing so, it is easy to record all the modification history of a document, and to merge modifications from different collaborators into one.

For a detailed explanation of OT, please refer to this document.

In our implementation, the document, which is a collection of OT operations, is stored on the server side using ShareDB, and served to the frontend using WebSocket API. ShareDB deals with the versioning of operations and handles the merging of them from different clients.

Quill editor on the client side receives the operations, or Delta as it claims, and renders them into HTML using a virtual DOM like tech called Parchment, which transforms operations into a hierarchy of Blots that represent paragraphs, texts and images. The Blots are converted to HTML and inserted into the webpage in the end.

Blots listen for the mutation records from the browser, and transforms the records into Delta. Quill sends the Delta to ShareDB to be merged and saved.

Authorship display

In the collaborative editing context, we often want to see the author of a certain paragraph, a sentence or even a word to be displayed along with the text. In our implementation, the author's id is recorded inside the document as class attributes. As the user typing in, the author's id is added automatically.

When there're more than 1 author inside the document, we will show a sidebar to display the author's name in a paragraph level. The author of a paragraph is decided by counting the number of characters that belongs to this author inside the paragraph.

We do not show authors information in the sentence level. However, it could be easily implemented using CSS.

Chinese/Japanese/Korean characters composition

For languages that requires composition such as Chinese, some temporary characters might be put into the editor by the composition tools during the composition process, at the end of the composition progress, the temp chars are deleted, and the real characters are inserted.

In the collaboration environment, during a composition process, there might be changes from other clients that are pushed to our editor, and changes the html when applied. The modification of the html elements during a composition process will break the mutation records and lead to the editor producing wrong Deltas.

We fix this issue by pausing the applying of deltas from upstream server and at the end of the composition process merge the pending upstream deltas with the real characters from composition.

The temp characters during the composition process will not be uploaded to the server so that the modification history will not become a mess.

Image uploading placeholder

When uploading images, there will be a placeholder showing the image (read from local file) and loading status. When the image is successfully uploaded, the image placeholder will be replaced with the uploaded one.

There're 3 ways user might insert image into the editor: the toolbar button, drag'n'drop from file explorer, and copy'n'paste from other web pages or applications, which are all taken good care of. The only thing left to do for the developers is to implement the uploading handler, uploads the image to the server and returns an image URL.

Local only delta

To support image uploading placeholder, which should only appear in our local editor and never get uploaded to the server, we extend Quill's functionality to add local only deltas to the editor, and the upstream changes will be transformed by those local only deltas before applied to our editor, and before the delta is uploaded to the server, local only deltas are removed. Applied local only deltas could be removed from the stack in any order at any time.

Getting Started

There's a demo included in this repo, to see it up and running and play with it yourself, follow the instructions in the Development section of this doc.


$ npm install --save miks-collaborative-editor


import Editor from "miks-collaborative-editor";
import 'quill/dist/quill.snow.css'

// The current user's info, must contain both id and name field. 
let author = {
    id: 10,
    name: 'Main Author'

let editorOptions = {
    authorship: {
        author: author,
        // The color used to highlight current user's paragraphs.
        authorColor: '#ed5634', 
        // The colors used to highlight other authors' paragraphs.
        colors: [
        handlers: {

            // Used to fetch a user's name when we find the id of the user
            // in the content.
            // Should always return a promise
            getAuthorInfoById: (authorId) => {
                return new Promise((resolve, reject) => {

                    let author = {
                        id: 12345,
                        name: 'Another author'

                    if(author) {
                        reject("user not found");
    image: {
        handlers: {

            // Upload image in DataURI format to the server
            // and return a URL to be used in the editor.
            // Should always return a promise
            imageDataURIUpload: (dataURI) => {


                return new Promise((resolve) => {

            // Send a external image url to the server
            // and return a URL in our own domain..
            // Usually we don't want to keep the external image src in the
            // editor and instead want to fetch it and save it on our own server.
            // Should always return a promise
            imageSrcUpload: (src) => {


                return new Promise((resolve) => {
            // Handle the display of image upload errors.
            imageUploadError: (err) => {
                console.log("image upload error: " + err);

// The editor toolbar configuration in the exact format as Quill
// Note that image upload button handling is already included
// no extra setup is required beyond the implementation of
// the image upload handlers above.
let toolbarOptions = [
    ['bold', 'italic', 'underline', 'strike'],
    [{'header': 1}, {'header': 2}, {'header': 3}],
    [{'list': 'ordered'}, {'list': 'bullet'}, {'indent': '+1'}, {'indent': '-1'}],
    ['align', 'color', 'background'],
    ['blockquote', 'code-block', 'link', 'image']

// Quill options
// Customize it as you want, just remember not to alter the handlers related
// to image uploading, clipboard image pasting and image drag'n'drop.
let quillOptions = {
    modules: {
        toolbar: toolbarOptions
    theme: 'snow'

let editor = new Editor("#container", editorOptions, quillOptions);

let websocketEndpoint = "ws://localhost:8080";
editor.syncThroughWebsocket(websocketEndpoint, "examples", "test-doc");

Content display

The content is stored as Delta in the backend database, which should be converted into HTML before rendering on a web page. For details please refer to the Development section.

Since Quill uses CSS to implement some of the functions such as list. The relevent CSS rules should also be added to the content displaying page. We extract the required CSS rules in display.styl file to be imported in the content displaying page. Import the file and add a class ql-editor to the parent element of HTML content to properly render the content. Check the demo for details.


There's a demo included in this repository to load the editor, which could also be used to do the development. The demo is located under demo directory.

Load the editor

Node modules should be installed first:

$ npm install

Then we need to start the server side websocket api so that our editor could connect to it and start running. A functional server side script is already included in the server directory.

$ node server/server.js

Running above command will start the websocket server on port 9001.

Last step is to start the demo using webpack:

$ npm start

Now you should be able to see a webpage popup with a loaded editor.

Display the content

Since the content is stored in Delta format, it must be converted into HTML before rendered on a web page. We could use Quill to do the converting. A demo is included in display.js. Open another browser tab and navigate to:

And you will see a web page with rendered HTML content displayed.


Any kind of contribution is welcome!

Don't hesitate! Submit your PR!

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