Method formatText

packages/quill/src/core/quill.ts:434–460

(
    index: number | Range,
    length: number | string,
    name: string | unknown,
    value?: unknown | EmitterSource,
    source?: EmitterSource,
  )

    source?: EmitterSource,
  ): Delta;
  formatText(
    index: number | Range,
    length: number | string,
    name: string | unknown,
    value?: unknown | EmitterSource,
    source?: EmitterSource,
  ): Delta {
    let formats: Record<string, unknown>;
    // eslint-disable-next-line prefer-const
    [index, length, formats, source] = overload(
      // @ts-expect-error
      index,
      length,
      name,
      value,
      source,
    );
    return modify.call(
      this,
      () => {
        return this.editor.formatText(index, length, formats);
      },
      source,
      index,
      0,
    );
  }

  getBounds(index: number | Range, length = 0): Bounds | null {
    let bounds: Bounds | null = null;