I am tryint yo understand some code from an opensource project that handles indexDB commands within a Google Chrome application.
The code is as follows :
var db = pm.indexedDB.db;
var trans = db.transaction([pm.indexedDB.TABLE_DRIVE_CHANGES], "readwrite");
var store = trans.objectStore(pm.indexedDB.TABLE_DRIVE_CHANGES);
var boundKeyRange = IDBKeyRange.only(driveChange.id);
var request = store.put(driveChange);
request.onsuccess = function (e) {
callback(driveChange);
};
request.onerror = function (e) {
console.log(e.value);
};
Although the app works, to me it seems that the following line is redundant code
var boundKeyRange = IDBKeyRange.only(driveChange.id);
Or am I missing something? The variable 'boundKeyRange' is never referenced anywhere.
Unless boundKeyRange is used later, you're not missing something. IDBKeyRange.only just creates an IDBKeyRange object, and if that object isn't used in some IndexedDB request, it does absolutely nothing.
Following HTML shows empty array in console on first click:
<!DOCTYPE html>
<html>
<head>
<script>
function test(){
console.log(window.speechSynthesis.getVoices())
}
</script>
</head>
<body>
Test
</body>
</html>
In second click you will get the expected list.
If you add onload event to call this function (<body onload="test()">), then you can get correct result on first click. Note that the first call on onload still doesn't work properly. It returns empty on page load but works afterward.
Questions:
Since it might be a bug in beta version, I gave up on "Why" questions.
Now, the question is if you want to access window.speechSynthesis on page load:
What is the best hack for this issue?
How can you make sure it will load speechSynthesis, on page load?
Background and tests:
I was testing the new features in Web Speech API, then I got to this problem in my code:
<script type="text/javascript">
$(document).ready(function(){
// Browser support messages. (You might need Chrome 33.0 Beta)
if (!('speechSynthesis' in window)) {
alert("You don't have speechSynthesis");
}
var voices = window.speechSynthesis.getVoices();
console.log(voices) // []
$("#test").on('click', function(){
var voices = window.speechSynthesis.getVoices();
console.log(voices); // [SpeechSynthesisVoice, ...]
});
});
</script>
<a id="test" href="#">click here if 'ready()' didn't work</a>
My question was: why does window.speechSynthesis.getVoices() return empty array, after page is loaded and onready function is triggered? As you can see if you click on the link, same function returns an array of available voices of Chrome by onclick triger?
It seems Chrome loads window.speechSynthesis after the page load!
The problem is not in ready event. If I remove the line var voice=... from ready function, for first click it shows empty list in console. But the second click works fine.
It seems window.speechSynthesis needs more time to load after first call. You need to call it twice! But also, you need to wait and let it load before second call on window.speechSynthesis. For example, following code shows two empty arrays in console if you run it for first time:
// First speechSynthesis call
var voices = window.speechSynthesis.getVoices();
console.log(voices);
// Second speechSynthesis call
voices = window.speechSynthesis.getVoices();
console.log(voices);
According to Web Speech API Errata (E11 2013-10-17), the voice list is loaded async to the page. An onvoiceschanged event is fired when they are loaded.
voiceschanged: Fired when the contents of the SpeechSynthesisVoiceList, that the getVoices method will return, have changed. Examples include: server-side synthesis where the list is determined asynchronously, or when client-side voices are installed/uninstalled.
So, the trick is to set your voice from the callback for that event listener:
// wait on voices to be loaded before fetching list
window.speechSynthesis.onvoiceschanged = function() {
window.speechSynthesis.getVoices();
...
};
You can use a setInterval to wait until the voices are loaded before using them however you need and then clearing the setInterval:
var timer = setInterval(function() {
var voices = speechSynthesis.getVoices();
console.log(voices);
if (voices.length !== 0) {
var msg = new SpeechSynthesisUtterance(/*some string here*/);
msg.voice = voices[/*some number here to choose from array*/];
speechSynthesis.speak(msg);
clearInterval(timer);
}
}, 200);
$("#test").on('click', timer);
After studying the behavior on Google Chrome and Firefox, this is what can get all voices:
Since it involves something asynchronous, it might be best done with a promise:
const allVoicesObtained = new Promise(function(resolve, reject) {
let voices = window.speechSynthesis.getVoices();
if (voices.length !== 0) {
resolve(voices);
} else {
window.speechSynthesis.addEventListener("voiceschanged", function() {
voices = window.speechSynthesis.getVoices();
resolve(voices);
});
}
});
allVoicesObtained.then(voices => console.log("All voices:", voices));
Note:
When the event voiceschanged fires, we need to call .getVoices() again. The original array won't be populated with content.
On Google Chrome, we don't have to call getVoices() initially. We only need to listen on the event, and it will then happen. On Firefox, listening is not enough, you have to call getVoices() and then listen on the event voiceschanged, and set the array using getVoices() once you get notified.
Using a promise makes the code more clean. Everything related to getting voices are in this promise code. If you don't use a promise but instead put this code in your speech routine, it is quite messy.
You can write a voiceObtained promise to resolve to a voice you want, and then your function to say something can just do: voiceObtained.then(voice => { }) and inside that handler, call the window.speechSynthesis.speak() to speak something. Or you can even write a promise speechReady("hello world").then(speech => { window.speechSynthesis.speak(speech) }) to say something.
heres the answer
function synthVoice(text) {
const awaitVoices = new Promise(resolve=>
window.speechSynthesis.onvoiceschanged = resolve)
.then(()=> {
const synth = window.speechSynthesis;
var voices = synth.getVoices();
console.log(voices)
const utterance = new SpeechSynthesisUtterance();
utterance.voice = voices[3];
utterance.text = text;
synth.speak(utterance);
});
}
At first i used onvoiceschanged , but it kept firing even after the voices was loaded, so my goal was to avoid onvoiceschanged at all cost.
This is what i came up with. It seems to work so far, will update if it breaks.
loadVoicesWhenAvailable();
function loadVoicesWhenAvailable() {
voices = synth.getVoices();
if (voices.length !== 0) {
console.log("start loading voices");
LoadVoices();
}
else {
setTimeout(function () { loadVoicesWhenAvailable(); }, 10)
}
}
setInterval solution by Salman Oskooi was perfect
Please see https://jsfiddle.net/exrx8e1y/
function myFunction() {
dtlarea=document.getElementById("details");
//dtlarea.style.display="none";
dtltxt="";
var mytimer = setInterval(function() {
var voices = speechSynthesis.getVoices();
//console.log(voices);
if (voices.length !== 0) {
var msg = new SpeechSynthesisUtterance();
msg.rate = document.getElementById("rate").value; // 0.1 to 10
msg.pitch = document.getElementById("pitch").value; //0 to 2
msg.volume = document.getElementById("volume").value; // 0 to 1
msg.text = document.getElementById("sampletext").value;
msg.lang = document.getElementById("lang").value; //'hi-IN';
for(var i=0;i<voices.length;i++){
dtltxt+=voices[i].lang+' '+voices[i].name+'\n';
if(voices[i].lang==msg.lang) {
msg.voice = voices[i]; // Note: some voices don't support altering params
msg.voiceURI = voices[i].voiceURI;
// break;
}
}
msg.onend = function(e) {
console.log('Finished in ' + event.elapsedTime + ' seconds.');
dtlarea.value=dtltxt;
};
speechSynthesis.speak(msg);
clearInterval(mytimer);
}
}, 1000);
}
This works fine on Chrome for MAC, Linux(Ubuntu), Windows and Android
Android has non-standard en_GB wile others have en-GB as language code
Also you will see that same language(lang) has multiple names
On Mac Chrome you get en-GB Daniel besides en-GB Google UK English Female and n-GB Google UK English Male
en-GB Daniel (Mac and iOS)
en-GB Google UK English Female
en-GB Google UK English Male
en_GB English United Kingdom
hi-IN Google हिन्दी
hi-IN Lekha (Mac and iOS)
hi_IN Hindi India
Another way to ensure voices are loaded before you need them is to bind their loading state to a promise, and then dispatch your speech commands from a then:
const awaitVoices = new Promise(done => speechSynthesis.onvoiceschanged = done);
function listVoices() {
awaitVoices.then(()=> {
let voices = speechSynthesis.getVoices();
console.log(voices);
});
}
When you call listVoices, it will either wait for the voices to load first, or dispatch your operation on the next tick.
I used this code to load voices successfully:
<select id="voices"></select>
...
function loadVoices() {
populateVoiceList();
if (speechSynthesis.onvoiceschanged !== undefined) {
speechSynthesis.onvoiceschanged = populateVoiceList;
}
}
function populateVoiceList() {
var allVoices = speechSynthesis.getVoices();
allVoices.forEach(function(voice, index) {
var option = $('<option>').val(index).html(voice.name).prop("selected", voice.default);
$('#voices').append(option);
});
if (allVoices.length > 0 && speechSynthesis.onvoiceschanged !== undefined) {
// unregister event listener (it is fired multiple times)
speechSynthesis.onvoiceschanged = null;
}
}
I found the 'onvoiceschanged' code from this article: https://hacks.mozilla.org/2016/01/firefox-and-the-web-speech-api/
Note: requires JQuery.
Works in Firefox/Safari and Chrome (and in Google Apps Script too - but only in the HTML).
async function speak(txt) {
await initVoices();
const u = new SpeechSynthesisUtterance(txt);
u.voice = speechSynthesis.getVoices()[3];
speechSynthesis.speak(u);
}
function initVoices() {
return new Promise(function (res, rej){
speechSynthesis.getVoices();
if (window.speechSynthesis.onvoiceschanged) {
res();
} else {
window.speechSynthesis.onvoiceschanged = () => res();
}
});
}
While the accepted answer works great but if you're using SPA and not loading full-page, on navigating between links, the voices will not be available.
This will run on a full-page load
window.speechSynthesis.onvoiceschanged
For SPA, it wouldn't run.
You can check if it's undefined, run it, or else, get it from the window object.
An example that works:
let voices = [];
if(window.speechSynthesis.onvoiceschanged == undefined){
window.speechSynthesis.onvoiceschanged = () => {
voices = window.speechSynthesis.getVoices();
}
}else{
voices = window.speechSynthesis.getVoices();
}
// console.log("voices", voices);
I had to do my own research for this to make sure I understood it properly, so just sharing (feel free to edit).
My goal is to:
Get a list of voices available on my device
Populate a select element with those voices (after a particular page loads)
Use easy to understand code
The basic functionality is demonstrated in MDN's official live demo of:
https://github.com/mdn/web-speech-api/tree/master/speak-easy-synthesis
but I wanted to understand it better.
To break the topic down...
SpeechSynthesis
The SpeechSynthesis interface of the Web Speech API is the controller
interface for the speech service; this can be used to retrieve
information about the synthesis voices available on the device, start
and pause speech, and other commands besides.
Source
onvoiceschanged
The onvoiceschanged property of the SpeechSynthesis interface
represents an event handler that will run when the list of
SpeechSynthesisVoice objects that would be returned by the
SpeechSynthesis.getVoices() method has changed (when the voiceschanged
event fires.)
Source
Example A
If my application merely has:
var synth = window.speechSynthesis;
console.log(synth);
console.log(synth.onvoiceschanged);
Chrome developer tools console will show:
Example B
If I change the code to:
var synth = window.speechSynthesis;
console.log("BEFORE");
console.log(synth);
console.log(synth.onvoiceschanged);
console.log("AFTER");
var voices = synth.getVoices();
console.log(voices);
console.log(synth);
console.log(synth.onvoiceschanged);
The before and after states are the same, and voices is an empty array.
Solution
Although i'm not confident implementing Promises, the following worked for me:
Defining the function
var synth = window.speechSynthesis;
// declare so that values are accessible globally
var voices = [];
function set_up_speech() {
return new Promise(function(resolve, reject) {
// get the voices
var voices = synth.getVoices();
// get reference to select element
var $select_topic_speaking_voice = $("#select_topic_speaking_voice");
// for each voice, generate select option html and append to select
for (var i = 0; i < voices.length; i++) {
var option = $("<option></option>");
var suffix = "";
// if it is the default voice, add suffix text
if (voices[i].default) {
suffix = " -- DEFAULT";
}
// create the option text
var option_text = voices[i].name + " (" + voices[i].lang + suffix + ")";
// add the option text
option.text(option_text);
// add option attributes
option.attr("data-lang", voices[i].lang);
option.attr("data-name", voices[i].name);
// append option to select element
$select_topic_speaking_voice.append(option);
}
// resolve the voices value
resolve(voices)
});
}
Calling the function
// in your handler, populate the select element
if (page_title === "something") {
set_up_speech()
}
Android Chrome - turn off data saver. It was helpfull for me.(Chrome 71.0.3578.99)
// wait until the voices load
window.speechSynthesis.onvoiceschanged = function() {
window.speechSynthesis.getVoices();
};
let voices = speechSynthesis.getVoices();
let gotVoices = false;
if (voices.length) {
resolve(voices, message);
} else {
speechSynthesis.onvoiceschanged = () => {
if (!gotVoices) {
voices = speechSynthesis.getVoices();
gotVoices = true;
if (voices.length) resolve(voices, message);
}
};
}
function resolve(voices, message) {
var synth = window.speechSynthesis;
let utter = new SpeechSynthesisUtterance();
utter.lang = 'en-US';
utter.voice = voices[65];
utter.text = message;
utter.volume = 100.0;
synth.speak(utter);
}
Works for Edge, Chrome and Safari - doesn't repeat the sentences.
UPDATE
I discovered the issue is that it's blocked. Despite the database always being created and upgraded by the same extension, it does not get closed. So now I'm getting the "onblocked" function called.
How do I "unblock" currently blocked databases? And how do I prevent this in the future? This is an app, so no tabs are using it. And since I can't open those databases to even delete them (this also gets blocked), how do I close them?
(For anyone wondering, to avoid this issue from the start, you HAVE to do the folllowing:)
mydb.onversionchange = function(event) {
mydb.close();
};
Original Post
IndexedDB dies and becomes unopenable if I (accidentally) try to open and upgrade with the wrong version. As far as I can tell, there's no way to ask indexedDB for the latest version of a DB. So if I try to run the following code twice, it destroys the database and it becomes unopenable:
And it never throws an error or calls onerror. It just sits silently
var db = null;
//Note, no version passed in, so the second time I do this, it seems to cause an error
var req = indexedDB.open( "test" );
req.onsuccess = function(event) { console.log( "suc: " + event.target.result.version ); db = event.target.result; };
req.onerror = function(event) { console.log( "err: " + event ); };
req.onupgradeneeded = function(event) { console.log( "upg: " + event.target.result.version ); };
//We're doing in interval since waiting for callback
var intv = setInterval(
function()
{
if ( db === null ) return;
clearInterval( intv );
var req2 = indexedDB.open( "test", db.version + 1 );
req2.onsuccess = function(event) { console.log( "suc: " + event.target.result.version ); };
req2.onerror = function(event) { console.log( "err: " + event ); };
req2.onupgradeneeded = function(event) { console.log( "upg: " + event.target.result.version ); };
},
50
);
All of that code is in my chrome.runtime.onInstalled.addListener. So when I update my app, it calls it again. If I call indexedDB.open( "test" ) without passing in the new version and then again run the setInterval function, it causes everything to become unusable and I'm never able to open "test" again. This would be solved if I could query indexedDB for the version of a database prior to attempting to open it. Does that exist?
Maybe this helps?
function getVersion(callback) {
var r = indexedDB.open('asdf');
r.onblocked = r.onerror = console.error;
r.onsuccess = function(event) {
event.target.result.close();
callback(event.target.result.version);
};
}
getVersion(function(version) {
console.log('The version is: %s', version);
});
Ok, based on the convo, this little util function might set you on the path:
var DATABASE_NAME_CONSTANT = 'whatever';
// Basic indexedDB connection helper
// #param callback the action to perform with the open connection
// #param version the version of the database to open or upgrade to
// #param upgradeNeeded the callback if the db should be upgraded
function connect(callback, version, upgradeNeeded) {
var r = indexedDB.open(DATABASE_NAME_CONSTANT, version);
if(upgradeNeeded) r.onupgradeneeded = updateNeeded;
r.onblocked = r.onerror = console.error;
r.onsuccess = function(event) {
console.log('Connected to %s version %s',
DATABASE_NAME_CONSTANT, version);
callback(event.target.result);
};
}
// Now let us say you needed to connect
// and need to have the version be upgraded
// and need to send in custom upgrades based on some ajax call
function fetch() {
var xhr = new XMLHttpRequest();
// ... setup the request and what not
xhr.onload = function(event) {
// if response is 200 etc
// store the json in some variable
var responseJSON = ...;
console.log('Fetched the json file successfully');
// Let's suppose you send in version and updgradeNeeded
// as properties of your fetched JSON object
var targetVersion = responseJSON.idb.targetVersion;
var upgradeNeeded = responseJSON.idb.upgradeNeeded;
// Now connect and do whatever
connect(function(db) {
// Do stuff with the locally scoped db variable
// For example, grab a prop from the fetched object
db.objectStore('asdf').put(responseJSON.recordToInsert);
// If you feel the need, but should not, close the db
db.close();
console.log('Finished doing idb stuff');
}, targetVersion, upgradeNeeded);
}
}
I think it is best to provide the version number always. If you don't how are you going to manage upgrades on the db structure? If you don't its a good chance you will get in a situation where same db versions on a client will have an other database structure, and I don't think that is the thing you want. So I would suggest to keep the version number in a variable.
Also when working with indexeddb you will have to provide an upgrade plan from al previous versions to the current. Meaning version 4 has a certain structure, but you will have to be able to get that same structure from scratch as from version 1,2 and 3
i started using this browser(chrome) feature.
i ve written a JS based on this , but the problem is even , it recognises the speech only once and ends . its not going continuously, i need to press the button again and again to start speech recognition . tell me where i should tweak . i ve set "recognition.continuous=true" still not helping ?
var recognition = new webkitSpeechRecognition();
recognition.continuous = true;
recognition.interimResults = true;
recognition.onstart = function() {
console.log("Recognition started");
};
recognition.onresult = function(event){
console.log(event.results);
};
recognition.onerror = function(e) {
console.log("Error");
};
recognition.onend = function() {
console.log("Speech recognition ended");
};
function start_speech() {
recognition.lang = 'en-IN'; // 'en-US' works too, as do many others
recognition.start();
}
I call "start_speech" from a button ! thats it
I know this is an old thread, but I had this problem too. I found that, even with the continuous flag set, if there are pauses in the input speech, a "no-speech" error gets thrown (triggers the onerror event) and the engine is shut down. I just added code in the onend to restart the engine:
recognition.onend = function() {
recognition.start();
};
The next problem you might get is, every time the engine restarts, the user has to re-grant permission to let the browser use the microphone. The only solution at this time seems to be to make sure you connect to your site over HTTPS (source: http://updates.html5rocks.com/2013/01/Voice-Driven-Web-Apps-Introduction-to-the-Web-Speech-API bottom of post in bold)
Perhaps the typo on this line:
recognition.continuos = true;
Should equal:
recognition.continuous = true;
recognition.onend = function(){
recognition.start();
// sets off a beep/noise each time it is accessed from a cell phone (Andoid).
// does NOT if accessed from a desktop (Windows using Chrome).
};
what's wrong with this code in Google Chrome
r = webkitIndexedDB.open(db_name,1);
r.onsuccess = success_callback;
r.onerror = error_callback;
r.onupgradeneeded = function(e){
var db = e.currentTarget.result;
db.createObjectStore('os_name',{keyPath:id,autoIncrement:true});
};
it's works in firefox (mozIndexedDB) but not in chrome. even onerror won't be triggered. anyway i get this error
Uncaught Error: NOT_FOUND_ERR: DOM IDBDatabase Exception 3
onupgradeneeded is not supported function in Google Chrome, instead you should use the setversion method for initiating the database in the beginning of onsuccess event on database opening as described here:
http://www.html5rocks.com/en/tutorials/indexeddb/todo/#toc-step2
Your code should look something like this:
r.onsuccess = function(e) {
var v = "1.0";
var db = e.currentTarget.result;
// We can only create Object stores in a setVersion transaction;
if(v!= db.version) {
var setVrequest = db.setVersion(v);
setVrequest.onfailure = error_callback;
setVrequest.onsuccess = function(e) {
var store = db.createObjectStore('os_name',{keyPath:id,autoIncrement:true});
...
};
}
...
}
Edit November 2013: This is a obsolete answer now, since Google Chrome only supports upgrade of the database with the onupgradeneeded event.