Implementing Voice Search In Susper (in Chrome only)

Last week @mariobehling opened up an issue to implement voice search in Susper. Google Chrome provides an API to integrate Speech recognition feature with any website. More about API can be read here: https://shapeshed.com/html5-speech-recognition-api/

The explanation might be in Javascript but it has been written following syntax of Angular 4 and Typescript. So, I created a speech-service including files:

  • speech-service.ts
  • speech-service.spec.ts

Code for speech-service.ts: This is the code which will control the working of voice search.

import { Injectable, NgZone } from ‘@angular/core’;
import { Observable } from ‘rxjs/Rx’;
interface
IWindow extends Window {
  webkitSpeechRecognition: any;
}
@Injectable()
export
class SpeechService {

constructor(private zone: NgZone) { }

record(lang: string): Observable<string> {
  return Observable.create(observe => {
    const { webkitSpeechRecognition }: IWindow = <IWindow>window;

    const recognition = new webkitSpeechRecognition();

    recognition.continuous = true;
    recognition.interimResults = true;
    recognition.onresult = take => this.zone.run(() => observe.next(take.results.item(take.results.length 1).item(0).transcript)
);

    recognition.onerror = err =>observe.error(err);
    recognition.onend = () => observe.complete();
    recognition.lang = lang;
    recognition.start();
});
}
}

You can find more details about API following the link which I have provided above in starting. Here recognition.onend() => observe.complete() works as an important role here. Many developers forget to use it when working on voice search feature. It works like: whenever a user stops speaking, it will automatically understand that voice action has now been completed and the search can be attempted. And for this:

speechRecognition() {
  this.speech.record(‘en_US’).subscribe(voice => this.onquery(voice));
}

We have used speechRecognition() function. onquery() function is called when a query is entered in a search bar.

Default language has been set up as ‘en_US’ i.e English. We also created an interface to link it with the API which Google Chrome provides for adding voice search feature on any website.

I have also used a separate module by name NgZone. Now, what is NgZone? It is used as an injectable service for executing working inside or outside of the Angular zone. I won’t go into detail about this module much here. More about it can be found on angular-docs website.

We have also, implemented a microphone icon on search bar similar to Google. This is how Susper’s homepage looks like now:

This feature only works in Google Chrome browser and for Firefox it doesn’t. So, for Firefox browser there was no need to show ‘microphone’ icon since voice search does not work Firefox. What we did simply use CSS code like this:

@mozdocument urlprefix() {
  .microphone {
    display: none;
  }
}

@-moz-document url-prefix() is used to target elements for Firefox browser only. Hence using, this feature we made it possible to hide microphone icon from Firefox and make it appear in Chrome.

For first time users: To use voice search feature click on the microphone feature which will trigger speechRecognition() function and will ask you permission to allow your laptop/desktop microphone to detect your voice. Once allowing it, we’re done! Now the user can easily, use voice search feature on Susper to search for a random thing.