A React component and hook to initiate a SpeechRecognition session

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Links

🔴 LIVE DEMO :red_circle:

Disclaimer

The Web Speech API is only supported by few browsers so far (see caniuse). If the API is not available, the Vocal component won't display anything.

This component intends to catch a speech result as soon as possible. This can be a good fit for vocal commands or search field filling. For now on it does not support continuous speech (see Roadmap below).
That means either a result is caught and returned or timeout is reached and the recognition is discarded.
The stop function returned by children-as-function mechanism allows to prematurely discard the recognition before timeout elapses.

Special cases

Some browsers supports the SpeechRecognition API but not all the related APIs.
For example, browsers on iOS 14.5, the SpeechGrammar and SpeechGrammarList and Permissions APIs are not supported.

Although the lack of SpeechGrammar and SpeechGrammarList is handled by the underlaying @untemps/vocal library, you need to deal with Permissions by yourself.

Installation

yarn add @untemps/react-vocal

Usage

Vocal component

Basic usage

import Vocal from '@untemps/react-vocal'

const App = () => {
	const [result, setResult] = useState('')

	const _onVocalStart = () => {
		setResult('')
	}

	const _onVocalResult = (result) => {
		setResult(result)
	}

	return (
		<div className="App">
			<span style={{ position: 'relative' }}>
				<Vocal
					onStart={_onVocalStart}
					onResult={_onVocalResult}
					style={{ width: 16, position: 'absolute', right: 10, top: -2 }}
				/>
				<input defaultValue={result} style={{ width: 300, height: 40 }} />
			</span>
		</div>
	)
}

---

Custom component

By default, Vocal displays an icon with two states:

• Idle
  
• Listening
  

But you can provide your own component.

• With a simple React element:

import Vocal from '@untemps/react-vocal'

const App = () => {
	return (
		<Vocal>
			<button>Start</button>
		</Vocal>
	)
}

In this case, a onClick handler is automatically attached to the component to start a recognition session.
Only the first direct descendant of Vocal will receive the onClick handler. If you want to use a more complex hierarchy, use the function syntax below.

• With a function that returns a React element:

import Vocal from '@untemps/react-vocal'

const Play = () => (
	<div
		style={{
			width: 0,
			height: 0,
			marginLeft: 1,
			borderStyle: 'solid',
			borderWidth: '4px 0 4px 8px',
			borderColor: 'transparent transparent transparent black',
		}}
	/>
)

const Stop = () => (
	<div
		style={{
			width: 8,
			height: 8,
			backgroundColor: 'black',
		}}
	/>
)

const App = () => {
	return (
		<Vocal>
			{(start, stop, isStarted) => (
				<button style={{ padding: 5 }} onClick={isStarted ? stop : start}>
					{isStarted ? <Stop /> : <Play />}
				</button>
			)}
		</Vocal>
	)
}

The following parameters are passed to the function:

Arguments	Type	Description
start	func	The function used to start the recognition
stop	func	The function used to stop the recognition
isStarted	bool	A flag that indicates whether the recognition is started or not

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Commands

The Vocal component accepts a commands prop to map special recognition results to callbacks.
That means you can define vocal commands to trigger specific functions.

const App = () => {
  return (
    <Vocal commands={{
      'switch border color': () => setBorderColor('red'),
    }}/>
  )
}

commands object is a key/pair model where the key is the command to be caught by the recognition and the value is the callback triggered when the command is detected.

key is not case sensitive.

const commands = {
    submit: () => submitForm(),
    'Change the background color': () => setBackgroundColor('red'), 
    'PLAY MUSIC': play
}

The component utilizes a special hook called useCommands to respond to the commands.
The hook performs a fuzzy search to match approximate commands if needed. This allows to fix accidental typos or approximate recognition results.
To do so the hook uses fuse.js which implements an algorithm to find strings that are approximately equal to a given input. The score precision that distinguishes acceptable command-to-callback mapping from negative matching can be customized in the hook instantiantion.

useCommands(commands, threshold) // threshold is the limit not to exceed to be considered a match

See fuze.js scoring theory for more details.

⚠️ The Vocal component doesn't expose that score yet. For now on you have to deal with the default value (0.4)

---

Vocal component API

Props	Type	Default	Description
commands	object	null	Callbacks to be triggered when specified commands are detected by the recognition
lang	string	'en-US'	Language understood by the recognition BCP 47 language tag
grammars	SpeechGrammarList	null	Grammars understood by the recognition JSpeech Grammar Format
timeout	number	3000	Time in ms to wait before discarding the recognition
style	object	null	Styles of the root element if className is not specified
className	string	null	Class of the root element
onStart	func	null	Handler called when the recognition starts
onEnd	func	null	Handler called when the recognition ends
onSpeechStart	func	null	Handler called when the speech starts
onSpeechEnd	func	null	Handler called when the speech ends
onResult	func	null	Handler called when a result is recognized
onError	func	null	Handler called when an error occurs
onNoMatch	func	null	Handler called when no result can be recognized

useVocal hook

Basic usage

import React, { useState } from 'react'
import { useVocal } from '@untemps/react-vocal'
import Icon from './Icon'

const App = () => {
	const [isListening, setIsListening] = useState(false)
	const [result, setResult] = useState('')

	const [, { start, subscribe }] = useVocal('fr_FR')

	const _onButtonClick = () => {
		setIsListening(true)

		subscribe('speechstart', _onVocalStart)
		subscribe('result', _onVocalResult)
		subscribe('error', _onVocalError)
		start()
	}

	const _onVocalStart = () => {
		setResult('')
	}

	const _onVocalResult = (result) => {
		setIsListening(false)

		setResult(result)
	}

	const _onVocalError = (e) => {
		console.error(e)
	}

	return (
		<div>
			<span style={{ position: 'relative' }}>
				<div
					role="button"
					aria-label="Vocal"
					tabIndex={0}
					style={{ width: 16, position: 'absolute', right: 10, top: 2 }}
					onClick={_onButtonClick}
				>
					<Icon color={isListening ? 'red' : 'blue'} />
				</div>
				<input defaultValue={result} style={{ width: 300, height: 40 }} />
			</span>
		</div>
	)
}

---

Signature

useVocal(lang, grammars)

Args	Type	Default	Description
lang	string	'en-US'	Language understood by the recognition BCP 47 language tag
grammars	SpeechGrammarList	null	Grammars understood by the recognition JSpeech Grammar Format

---

Return value

const [ref, { start, stop, abort, subscribe, unsubscribe, clean }]

Args	Type	Description
ref	Ref	React ref to the SpeechRecognitionWrapper instance
start	func	Function to start the recognition
stop	func	Function to stop the recognition
abort	func	Function to abort the recognition
subscribe	func	Function to subscribe to recognition events
unsubscribe	func	Function to unsubscribe to recognition events
clean	func	Function to clean subscription to recognition events

Browser support flag

Basic usage

import Vocal, { isSupported } from '@untemps/react-vocal'

const App = () => {
	return isSupported ? <Vocal /> : <p>Your browser does not support Web Speech API</p>
}

Events

Events	Description
audioend	Fired when the user agent has finished capturing audio for recognition
audiostart	Fired when the user agent has started to capture audio for recognition
end	Fired when the recognition service has disconnected
error	Fired when a recognition error occurs
nomatch	Fired when the recognition service returns a final result with no significant recognition
result	Fired when the recognition service returns a result
soundend	Fired when any sound — recognisable or not — has stopped being detected
soundstart	Fired when any sound — recognisable or not — has been detected
speechend	Fired when speech recognized by the recognition service has stopped being detected
speechstart	Fired when sound recognized by the recognition service as speech has been detected
start	fired when the recognition service has begun listening to incoming audio

Notes

The process to grant microphone access permissions is automatically managed by the hook (internally used by the Vocal component).

Development

The component can be served for development purpose on http://localhost:10001/ using:

yarn dev

Contributing

Contributions are warmly welcomed:

• Fork the repository
• Create a feature branch (preferred name convention: [feature type]_[imperative verb]-[description of the feature])
• Develop the feature AND write the tests (or write the tests AND develop the feature)
• Commit your changes using Angular Git Commit Guidelines
• Submit a Pull Request

Roadmap

• Add a connector management to plug external speech-to-text services in
• Support continuous speech