diff --git a/index.d.ts b/index.d.ts
index eb539aa..3073395 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,82 +1,117 @@
-import * as RN from 'react-native'
+import * as RN from "react-native";
 
-type SimpleEvents = 'tts-start' | 'tts-finish' | 'tts-error' | 'tts-cancel'
+type SimpleEvents = "tts-start" | "tts-finish" | "tts-error" | "tts-cancel";
 type SimpleEvent = {
-  utteranceId: string | number
-}
+  utteranceId: string | number;
+};
 
-type ProgressEventName = 'tts-progress'
+type ProgressEventName = "tts-progress";
 type ProgressEvent = {
-  utteranceId: string | number
-  location: number
-  length: number
-}
+  utteranceId: string | number;
+  location: number;
+  length: number;
+};
 
-export type TtsEvents = SimpleEvents | ProgressEventName
-export type TtsEvent<T extends TtsEvents = TtsEvents> = T extends ProgressEventName ? ProgressEvent : SimpleEvent
-export type TtsEventHandler<T extends TtsEvents= TtsEvents> = (event: TtsEvent<T>) => any
+export type TtsEvents = SimpleEvents | ProgressEventName;
+export type TtsEvent<
+  T extends TtsEvents = TtsEvents
+> = T extends ProgressEventName ? ProgressEvent : SimpleEvent;
+export type TtsEventHandler<T extends TtsEvents = TtsEvents> = (
+  event: TtsEvent<T>
+) => any;
 
 export type TtsError = {
-  code: 'no_engine' | 'error' | 'not_ready' | 'invalid_request' | 'network_error' | 'network_timeout' | 'not_installed_yet' | 'output_error'
-  | 'service_error' | 'synthesis_error' | 'lang_missing_data' | 'lang_not_supported' | 'Android AudioManager error' | 'not_available' | 'not_found'
-  | 'bad_rate'
-  message: string
-}
+  code:
+    | "no_engine"
+    | "error"
+    | "not_ready"
+    | "invalid_request"
+    | "network_error"
+    | "network_timeout"
+    | "not_installed_yet"
+    | "output_error"
+    | "service_error"
+    | "synthesis_error"
+    | "lang_missing_data"
+    | "lang_not_supported"
+    | "Android AudioManager error"
+    | "not_available"
+    | "not_found"
+    | "bad_rate";
+  message: string;
+};
 
 export type Voice = {
-  id: string
-  name: string
-  language: string
-  quality: number
-  latency: number
-  networkConnectionRequired: boolean
-  notInstalled: boolean
-}
+  id: string;
+  name: string;
+  language: string;
+  quality: number;
+  latency: number;
+  networkConnectionRequired: boolean;
+  notInstalled: boolean;
+};
 
 export type Engine = {
-  name: string
-  label: string
-  default: boolean
-  icon: number
-}
+  name: string;
+  label: string;
+  default: boolean;
+  icon: number;
+};
 
 export type AndroidOptions = {
   /** Parameter key to specify the audio stream type to be used when speaking text or playing back a file */
-  KEY_PARAM_STREAM: 'STREAM_VOICE_CALL' | 'STREAM_SYSTEM' | 'STREAM_RING' | 'STREAM_MUSIC' | 'STREAM_MUSIC' | 'STREAM_ALARM' | 'STREAM_NOTIFICATION' | 'STREAM_DTMF' | 'STREAM_ACCESSIBILITY'
+  KEY_PARAM_STREAM:
+    | "STREAM_VOICE_CALL"
+    | "STREAM_SYSTEM"
+    | "STREAM_RING"
+    | "STREAM_MUSIC"
+    | "STREAM_MUSIC"
+    | "STREAM_ALARM"
+    | "STREAM_NOTIFICATION"
+    | "STREAM_DTMF"
+    | "STREAM_ACCESSIBILITY";
   /** Parameter key to specify the speech volume relative to the current stream type volume used when speaking text. Volume is specified as a float ranging from 0 to 1 where 0 is silence, and 1 is the maximum volume (the default behavior). */
-  KEY_PARAM_VOLUME: number
+  KEY_PARAM_VOLUME: number;
   /** Parameter key to specify how the speech is panned from left to right when speaking text. Pan is specified as a float ranging from -1 to +1 where -1 maps to a hard-left pan, 0 to center (the default behavior), and +1 to hard-right. */
-  KEY_PARAM_PAN: number
-}
+  KEY_PARAM_PAN: number;
+};
 
-export type Options = string | {
-  iosVoiceId: string
-  rate: number
-  androidParams: AndroidOptions
-}
+export type Options =
+  | string
+  | {
+      iosVoiceId: string;
+      rate: number;
+      androidParams: AndroidOptions;
+    };
 
 export class ReactNativeTts extends RN.NativeEventEmitter {
-  getInitStatus: () => Promise<'success'>
-  requestInstallEngine: () => Promise<'success'>
-  requestInstallData: () => Promise<'success'>
-  setDucking: (enabled: boolean) => Promise<'success'>
-  setDefaultEngine: (engineName: string) => Promise<boolean>
-  setDefaultVoice: (voiceId: string) => Promise<'success'>
-  setDefaultRate: (rate: number, skipTransform?: boolean) => Promise<'success'>
-  setDefaultPitch: (pitch: number) => Promise<'success'>
-  setDefaultLanguage: (language: string) => Promise<'success'>
-  setIgnoreSilentSwitch: (ignoreSilentSwitch: boolean) => Promise<boolean>
-  voices: () => Promise<Voice[]>
-  engines: () => Promise<Engine[]>
+  getInitStatus: () => Promise<"success">;
+  requestInstallEngine: () => Promise<"success">;
+  requestInstallData: () => Promise<"success">;
+  setDucking: (enabled: boolean) => Promise<"success">;
+  setDefaultEngine: (engineName: string) => Promise<boolean>;
+  setDefaultVoice: (voiceId: string) => Promise<"success">;
+  setDefaultRate: (rate: number, skipTransform?: boolean) => Promise<"success">;
+  setDefaultPitch: (pitch: number) => Promise<"success">;
+  setDefaultLanguage: (language: string) => Promise<"success">;
+  setIgnoreSilentSwitch: (ignoreSilentSwitch: boolean) => Promise<boolean>;
+  voices: () => Promise<Voice[]>;
+  engines: () => Promise<Engine[]>;
   /** Read the sentence and return an id for the task. */
-  speak: (utterance: string, options?: Options) => string | number
-  stop: (onWordBoundary?: boolean) => Promise<boolean>
-  pause: (onWordBoundary?: boolean) => Promise<boolean>
-  resume: () => Promise<boolean>
-  addEventListener: <T extends TtsEvents>(type: T, handler: TtsEventHandler<T>) => void
-  removeEventListener: <T extends TtsEvents>(type: T, handler: TtsEventHandler<T>) => void
+  speak: (utterance: string, options?: Options) => string | number;
+  stop: (onWordBoundary?: boolean) => Promise<boolean>;
+  pause: (onWordBoundary?: boolean) => Promise<boolean>;
+  resume: () => Promise<boolean>;
+  addEventListener: <T extends TtsEvents>(
+    type: T,
+    handler: TtsEventHandler<T>
+  ) => void;
+  removeEventListener: <T extends TtsEvents>(
+    type: T,
+    handler: TtsEventHandler<T>
+  ) => void;
 }
 
-declare const Tts = new ReactNativeTts();
+declare const Tts: ReactNativeTts;
 
-export default Tts
+export default Tts;