const List = Quill.import('formats/list');
const ListItem = Quill.import('formats/list/item');
const Parchment = Quill.import('parchment');
const Module = Quill.import('core/module');

class TaskListItem extends ListItem {
  format(name, value) {
    if (name === TaskList.blotName && !value) {
      this.replaceWith(Parchment.create(this.statics.scope));
    }
    else {
      super.format(name, value);
    }
  }

  // when inserting a new list item, remove the 'checked' css class
  clone() {
    const clone = super.clone();
    clone.domNode.classList.remove('checked');
    return clone;
  }
}

TaskListItem.blotName = 'task-list-item';
TaskListItem.tagName = 'LI';

class TaskList extends List {
  static create(value) {
    return super.create('bullet');
  }

  static formats(domNode) {
    return 'bullet';
  }
}

TaskList.blotName = 'task-list';
TaskList.tagName = 'UL';
TaskList.className = 'task-list';
TaskList.defaultChild = 'task-list-item';
TaskList.allowedChildren = [TaskListItem];

class TaskListModule extends Module {
  constructor(quill, options) {
    super(quill, options);

    this.onClick = options.onClick || function() {};

    this.quill.container.addEventListener('click', (e) => {
      if (e.target.matches('ul.task-list > li')) {
        e.target.classList.toggle('checked');
        this.onClick();
      }
    });
  }
}

Quill.register({
  'formats/task-list': TaskList,
  'formats/task-list/item': TaskListItem,
  'modules/task-list': TaskListModule
});

Quill.import('ui/icons')['task-list'] = `
  <svg class="" viewbox="0 0 18 18">
    <line class="ql-stroke" x1="9" x2="15" y1="4" y2="4"></line>
    <polyline class="ql-stroke" points="3 4 4 5 6 3"></polyline>
    <line class="ql-stroke" x1="9" x2="15" y1="14" y2="14"></line>
    <polyline class="ql-stroke" points="3 14 4 15 6 13"></polyline>
    <line class="ql-stroke" x1="9" x2="15" y1="9" y2="9"></line>
    <polyline class="ql-stroke" points="3 9 4 10 6 8"></polyline>
  </svg>
`;

@@ -1488,16 +1488,93 @@
 le%0A%7D);%0A%0A
+// https://github.com/quilljs/quill/blob/develop/assets/icons/list-check.svg%0A
 Quill.im

document source of svg icon