Reference version

Archive Expo Snack Discord and Forums Newsletter

Expo Speech

GitHub

npm

A library that provides access to text-to-speech functionality.

expo-speech provides an API that allows you to utilize Text-to-speech functionality in your app.

Platform Compatibility

Android Device	Android Emulator	iOS Device	iOS Simulator	Web

Installation

Terminal

- npx expo install expo-speech

If you are installing this in an existing React Native app, start by installing expo in your project. Then, follow the additional instructions as mentioned by the library's README under "Installation in bare React Native projects" section.

Usage

Speech

import { View, StyleSheet, Button } from 'react-native';
import * as Speech from 'expo-speech';

export default function App() {
  const speak = () => {
    const thingToSay = '1';
    Speech.speak(thingToSay);
  };

  return (
    <View style={styles.container}>
      <Button title="Press to hear some words" onPress={speak} />
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    backgroundColor: '#ecf0f1',
    padding: 8,
  },
});

API

import * as Speech from 'expo-speech';

Constants

`Speech.maxSpeechInputLength`

Type: number

Maximum possible text length acceptable by Speech.speak() method. It is platform-dependent. On iOS, this returns Number.MAX_VALUE.

Methods

`Speech.getAvailableVoicesAsync()`

Returns list of all available voices.

Returns:

Promise<Voice[]>

List of Voice objects.

`Speech.isSpeakingAsync()`

Determine whether the Text-to-speech utility is currently speaking. Will return true if speaker is paused.

Returns:

Promise<boolean>

Returns a Promise that fulfils with a boolean, true if speaking, false if not.

`Speech.pause()`

Pauses current speech. This method is not available on Android.

Returns:

Promise<void>

`Speech.resume()`

Resumes speaking previously paused speech or does nothing if there's none. This method is not available on Android.

Returns:

Promise<void>

`Speech.speak(text, options)`

Parameter	Type	Description
text	`string`	The text to be spoken. Cannot be longer than `Speech.maxSpeechInputLength`.
options (optional)	`SpeechOptions`	A `SpeechOptions` object. Default:`{}`

Speak out loud the text given options. Calling this when another text is being spoken adds an utterance to queue.

Returns:

void

`Speech.stop()`

Interrupts current speech and deletes all in queue.

Returns:

Promise<void>

Types

`SpeechEventCallback()`

Parameter	Type
this	`SpeechSynthesisUtterance`
ev	`SpeechSynthesisEvent`

Returns:

any

`SpeechOptions`

Name	Type	Description
_voiceIndex (optional)	`number`	-
language (optional)	`string`	The code of a language that should be used to read the `text`, refer to IETF BCP 47 to see valid codes.
onBoundary (optional)	`NativeBoundaryEventCallback \| SpeechEventCallback \| null`	A callback that is invoked when the spoken utterance reaches a word.
onDone (optional)	`() => void \| SpeechEventCallback`	A callback that is invoked when speaking finishes.
onError (optional)	`(error: Error) => void \| SpeechEventCallback`	Only for: Android iOS A callback that is invoked when an error occurred while speaking.
onMark (optional)	`SpeechEventCallback \| null`	-
onPause (optional)	`SpeechEventCallback \| null`	-
onResume (optional)	`SpeechEventCallback \| null`	-
onStart (optional)	`() => void \| SpeechEventCallback`	A callback that is invoked when speaking starts.
onStopped (optional)	`() => void \| SpeechEventCallback`	A callback that is invoked when speaking is stopped by calling `Speech.stop()`.
pitch (optional)	`number`	Pitch of the voice to speak `text`. `1.0` is the normal pitch.
rate (optional)	`number`	Rate of the voice to speak `text`. `1.0` is the normal rate.
voice (optional)	`string`	Voice identifier.
volume (optional)	`number`	Only for: Web Volume of the voice to speak `text`. A number between `0.0` (muted) and `1.0` (max volume) Default:`1.0`

`Voice`

Object describing the available voices on the device.

Name	Type	Description
identifier	`string`	Voice unique identifier.
language	`string`	Voice language.
name	`string`	Voice name.
quality	`VoiceQuality`	Voice quality.

`WebVoice`

Type: Voice extended by:

Name	Type	Description
isDefault	`boolean`	-
localService	`boolean`	-
name	`string`	-
voiceURI	`string`	-

Enums

`VoiceQuality`

Enum representing the voice quality.

`Default`

VoiceQuality.Default ＝ "Default"

`Enhanced`

VoiceQuality.Enhanced ＝ "Enhanced"