How to use the quill/core/emitter.events function in quill

constructor(quill, bounds) {
    super(quill, bounds);
    this.quill.on(Emitter.events.EDITOR_CHANGE, (type, range, oldRange, source) => {
      if (type !== Emitter.events.SELECTION_CHANGE) return;
      if (range != null && range.length > 0 && source === Emitter.sources.USER) {
        this.show();
        // Lock our width so we will expand beyond our offsetParent boundaries
        this.root.style.left = '0px';
        this.root.style.width = '';
        this.root.style.width = this.root.offsetWidth + 'px';
        let lines = this.quill.getLines(range.index, range.length);
        if (lines.length === 1) {
          this.position(this.quill.getBounds(range));
        } else {
          let lastLine = lines[lines.length - 1];
          let index = this.quill.getIndex(lastLine);
          let length = Math.min(lastLine.length() - 1, range.index + range.length - index);
          let bounds = this.quill.getBounds(new Range(index, length));
          this.position(bounds);

listen() {
    super.listen();
    this.root.querySelector('.ql-close').addEventListener('click', () => {
      this.root.classList.remove('ql-editing');
    });
    this.quill.on(Emitter.events.SCROLL_OPTIMIZE, () => {
      // Let selection be restored by toolbar handlers before repositioning
      setTimeout(() => {
        if (this.root.classList.contains('ql-hidden')) return;
        let range = this.quill.getSelection();
        if (range != null) {
          this.position(this.quill.getBounds(range));
        }
      }, 1);
    });
  }

this.quill.on(Emitter.events.EDITOR_CHANGE, (type, range, oldRange, source) => {
      if (type !== Emitter.events.SELECTION_CHANGE) return;
      if (range != null && range.length > 0 && source === Emitter.sources.USER) {
        this.show();
        // Lock our width so we will expand beyond our offsetParent boundaries
        this.root.style.left = '0px';
        this.root.style.width = '';
        this.root.style.width = this.root.offsetWidth + 'px';
        let lines = this.quill.getLines(range.index, range.length);
        if (lines.length === 1) {
          this.position(this.quill.getBounds(range));
        } else {
          let lastLine = lines[lines.length - 1];
          let index = this.quill.getIndex(lastLine);
          let length = Math.min(lastLine.length() - 1, range.index + range.length - index);
          let bounds = this.quill.getBounds(new Range(index, length));
          this.position(bounds);
        }

} else {
        this.edit('link', this.preview.textContent);
      }
      event.preventDefault();
    });
    this.root.querySelector('a.ql-remove').addEventListener('click', (event) => {
      if (this.linkRange != null) {
        let range = this.linkRange;
        this.restoreFocus();
        this.quill.formatText(range, 'link', false, Emitter.sources.USER);
        delete this.linkRange;
      }
      event.preventDefault();
      this.hide();
    });
    this.quill.on(Emitter.events.SELECTION_CHANGE, (range, oldRange, source) => {
      if (range == null) return;
      if (range.length === 0 && source === Emitter.sources.USER) {
        let [link, offset] = this.quill.scroll.descendant(LinkBlot, range.index);
        if (link != null) {
          this.linkRange = new Range(range.index - offset, link.length());
          let preview = LinkBlot.formats(link.domNode);
          this.preview.textContent = preview;
          this.preview.setAttribute('href', preview);
          this.show();
          this.position(this.quill.getBounds(this.linkRange));
          return;
        }
      } else {
        delete this.linkRange;
      }
      this.hide();

setupSelectionListener() {
        this.quill.on(Emitter.events.EDITOR_CHANGE, this.handleEditorChange);
    }

fillSelect(select, FONTS);
          } else if (select.classList.contains('ql-header')) {
            fillSelect(select, HEADERS);
          } else if (select.classList.contains('ql-size')) {
            fillSelect(select, SIZES);
          }
        }
        return new Picker(select);
      }
    });
    let update = () => {
      this.pickers.forEach(function(picker) {
        picker.update();
      });
    };
    this.quill.on(Emitter.events.EDITOR_CHANGE, update);
  }