I am writing a chat AJAX app. Randomly, in FF 3.5.9, setInterval() seems to stop firing. I don't have clearInterval() anywhere in my code. What could be causing this to happen?
$(document).ready(function () {
$("#no-js-warning").empty();
messageRefresher = new MessageRefresher(0);
setInterval($.proxy(messageRefresher, "refresh"), 2000);
});
function notifyInRoom(user) {
$.getJSON('API/users_in_room', { room_id: $.getUrlVar('key'), username: user }, function (users) {
if (!$.isEmptyObject(users)) {
$("#users").empty();
$.each(users, function (index, username) {
var newChild = sprintf("<li>%s</li>", username);
$("#users").append(newChild);
});
}
else {
$("#users-loading-msg").text("No one is in this room.");
}
});
}
function MessageRefresher(latest_mid) {
this._latest_mid = latest_mid;
}
MessageRefresher.prototype.refresh = function () {
notifyInRoom($("#user-name").val());
var refresher = this;
$.getJSON('API/read_messages', { room_id: $.getUrlVar('key'), mid: refresher._latest_mid }, function (messages) {
if (! (messages == null || $.isEmptyObject(messages[0]))) { // messages will always be at least [[], [], 0]
$("#messages-loading-msg").hide();
for (var i = 0; i < messages[0].length; i++) {
var newChild = sprintf('<li><span class="username">%s:</span> %s</li>', messages[1][i], messages[0][i]);
$("#messages").append(newChild);
}
refresher._latest_mid = messages[2];
setUserBlockClass();
}
else {
$("#messages-loading-msg").text("No messages here. Say anything...");
}
});
}
// Give the end-user-block class to the appropriate messages
// eg, those where the next message is by a different user
function setUserBlockClass() {
$("#messages li").each(function (index) {
if ($(this).children(".username").text() != $(this).next().children(".username").text()) {
$(this).addClass("end-user-block");
}
});
}
I checked the most recent responses in Firebug, and it was the same responses that had been sent earlier. (So, it's not like an unusual response caused a crash.)
If I refresh the page, the calls resume.
I'm setting breakpoints in Firebug while I develop, then unsetting them and hitting "continue". Is there any chance that this is causing the problem? UPDATE: With more testing, this seems like it might be the issue.
I'm also using the service in another browser, and the calls continue fine for it.
I'm seeing setInterval getting stopped when I debug with Firebug. Assume it's a timing/interrupt thing as it works fine as long as I'm not stepping over breakpoints.
One thing to check that I just ran into was that if you are checking whether setInterval works with something like:
console.log("X");
Firebug will only display the 'X' one time. Firebug appears to refuse to log the same text twice. However, testing in the Chrome console worked fine.
When I changed my test code to:
console.log(new Date());
Firebug gave me the results I expected.
Related
I'm using web BLE. I have based my code according to the example of the heart rate measurement.
Everything is working fine most of the time. But sometimes, even if the connection is successfully made, when I try to bind to the notification, it doesn't work.
The link is made in this function :
_startNotifications(characteristicUuid) {
let characteristic = this._characteristics.get(characteristicUuid);
console.log(characteristic);
return characteristic.startNotifications().then(() => characteristic);
}
When everything is OK, I can see in the console that BluetoothRemoteGATTCharacteristic has a value : DataView(2) {}
Otherwise, when it's not working it has a value : null
I would like to be able to retry automatically, if I detect that the value is null. But I'm not familiar with Promise (I think this is it) and console.log(characteristic.value) doesn't work here.
How would you approach this ?
What I ended up doing is "bypass" the issue. So it's a more algorithmic resolution than a pure Javascript one.
I didn't change the connection function, so it is still called like this :
device._startNotifications(some_uuid).then(handleHeartRateMeasurement)
I check everything in the handleHeartRateMeasurement function :
var ready = false;
function handleHeartRateMeasurement(heartRateMeasurement) {
console.log("Hold on...");
heartRateMeasurement.addEventListener("characteristicvaluechanged", event => {
// Everytime the value change, this should be triggered
// If it did not, variable "ready" will stay false
ready = true;
var value = device.parseValue(event.target.value);
// Do something with value here
});
var check = function(){
// If we have received data from characteristic, we are ready to go !
if(ready === false){
console.log("Device connected but not receiving data");
// Stop the current notification subscription
device.stopNotificationsHeartRateMeasurement();
// Start a new one
device._startNotifications(some_uuid).then(handleHeartRateMeasurement);
setTimeout(check, 1000); // check again in a 1s
}
else{
console.log("Device connected and receiving data");
}
}
setTimeout(() => {
check();
}, 500);
}
I am making a chrome extension, and I am using chrome storage to store a variable. Actually I am first inputing a timer from user, and then refreshing the page after every T seconds those are given as input by user. So to store this time I used chrome storage like this :
chrome.extension.onMessage.addListener(function(request, sender, sendResponse) {
var currentTimer = request.timer;
if(currentTimer!=null){
currentTimer = currentTimer*1000;
alert(currentTimer);
chrome.storage.sync.set({'x': currentTimer}, function() {
console.log(currentTimer);
});
}
if(currentTimer==null){
chrome.storage.sync.get('x', function(items){
currentTimer = items.value;
});
//Here currentTimer is undefined.
}
});
Can anyone help why currentTimer is still undefined. I am debugging for very long time, but could not arrive at a solution.
The problem is that as soon as page is refreshed currentTimer will get NULL value as it is been entered only once by user.
All chrome.* API callbacks are invoked asynchronously when the originating function has already finished, which also means that the next statement after chrome.* API call is executed before the callback.
Put the code that needs the result into the callback:
chrome.storage.sync.get('something', function(item) {
setTimeout(someFunction, item.value);
});
In case the result is needed in a content script, return the value in a new message:
content script:
chrome.runtime.sendMessage({request: "doSomething"});
chrome.runtime.onMessage.addListener(function(msg) {
if (msg.response) {
// do something with the received msg.response
}
});
background script:
chrome.runtime.onMessage.addListener(function(msg, sender, sendResponse) {
if (msg.request == "doSomething") {
var tabId = sender.tab.id, frameId = sender.frameId;
chrome.storage.sync.get('something', function(item) {
sendMessageToFrameId(tabId, frameId, {response: item.value});
});
}
});
function sendMessageToFrameId(tabId, frameId, msg) {
// 1. frameId works since Chrome 41 and throws on prior versions
// 2. without frameId Chrome 45 sends the message to wrong tabs
try { chrome.tabs.sendMessage(tabId, msg, {frameId: frameId}); }
catch(e) { chrome.tabs.sendMessage(tabId, msg); }
}
I am attempting to build a webapp on a Chromebook, I need it to read RFID card serial numbers with an ACR122U NFC. I am using chrome-nfc.
I am reading cards happily, but I do not know how to fire an event when a card is presented.
Are there any events in chrome-nfc I can use to know when a card has been presented to the reader?
EDIT: I have been trying to use chrome.nfc.wait_for_tag, but it does not behave as I would expect.
// With a card on the reader
chrome.nfc.wait_for_tag(device, 10000, function(tag_type, tag_id){
var CSN = new Uint32Array(tag_id)[0];
console.log ( "CSN: " + CSN );
});
[DEBUG] acr122_set_timeout(round up to 1275 secs)
DEBUG: InListPassiveTarget SENS_REQ(ATQA)=0x4, SEL_RES(SAK)=0x8
DEBUG: tag_id: B6CA9B6B
DEBUG: found Mifare Classic 1K (106k type A)
[DEBUG] nfc.wait_for_passive_target: mifare_classic with ID: B6CA9B6B
CSN: 1805372086
// with no card on the reader
chrome.nfc.wait_for_tag(device, 10000, function(tag_type, tag_id){
var CSN = new Uint32Array(tag_id)[0];
console.log ( "CSN: " + CSN );
});
[DEBUG] acr122_set_timeout(round up to 1275 secs)
DEBUG: found 0 target, tg=144
Both return the results as above immediately, it does not seem to matter what number I use for a timeout...
If I call the function with no card on the reader, and then immediately put the card on the reader after function call, I get no output in the console.
I'm not familiar with chrome-nfc, but taking a shot in the dark by reverse engineering the source, it looks like you would want to use the wait_for_tag method, like:
chrome.nfc.wait_for_tag(device, 3000, function(tag_type, tag_id) {
// Do your magic here.
});
...Where device is your reader, 3000 is the maximum time to wait (in ms), and replacing // Do your magic here. with your desired logic. If it times out, both tag_type and tag_id will be null.
If you wanted to wait indefinitely, you could just recursively call a function with the above code. Example:
function waitAllDay(device) {
chrome.nfc.wait_for_tag(device, 1000, function(tag_type, tag_id) {
if(tag_type !== null && tag_id !== null)
{
// Do your magic here.
}
waitAllDay(device);
});
}
That's assuming you want it to continue waiting even after a tag has been presented. Wrap the waitAllDay(device); in an else if you want it to stop once a tag is read.
UPDATE: It seems the wait_for_tag method does not work as intended, so I'm proposing a second solution. I'm leaving the existing solution in place in case the method is fixed by the developers of chrome-nfc.
Another thing to try is to use chrome.nfc.read, passing in a timeout option, inside a window.setInterval.
var timer = window.setInterval(function () {
chrome.nfc.read(device, { timeout: 1000 }, function(type, ndef) {
if(!!type && !!ndef) {
// Do your magic here.
// Uncomment the next line if you want it to stop once found.
// window.clearInterval(timer);
}
});
}, 1000);
Be sure and call window.clearInterval(timer) whenever you want it to stop watching for tags.
While I do not consider this a proper solution; here is a workaround I am using for the time being.
function listen_for_tag(callback, listen_timeout){
var poll_delay = 400; //ms
var listen_loop = null;
if(!listen_timeout){
listen_timeout = 99999999;
}
function check_for_tag(){
if(listen_timeout < 0) {
clearInterval(listen_loop);
console.log("we didnt find a tag. finished");
}
chrome.nfc.wait_for_tag(dev_manager.devs[0].clients[0], 10, function(tag_type, tag_id){
console.log ( "FOUND A TAG!!" );
clearInterval(listen_loop);
// handle the callback (call it now)
var C = callback;
if (C) {
callback = null;
window.setTimeout(function() {
C(tag_type, tag_id);
}, 0);
}
});
listen_timeout -= poll_delay;
}
listen_loop = setInterval(check_for_tag, poll_delay);
}
I'm working with some pretty old code and the following is being used to monitor session status. If the user is inactive for X minutes (determined by check_session.php), they are logged out.
The server side stuff works fine. Actually, the existing javascript appears to work OK as well, but looks like it needs cleaning up.
Here's the existing javascript:
function checkSessionStatus()
{
session_http.open('GET', '/check_session.php', true);
session_http.onreadystatechange = handleSessionHttpResponse;
session_http.send(null);
}
function handleSessionHttpResponse()
{
if (session_http.readyState == 4)
{
results = session_http.responseText;
if (results == 'inactive')
{
window.location='/logout.php';
document.getElementById('session_divbox').innerHTML = results;
}
}
}
function get_session_HTTPObject()
{
var xml_session_http;
if (!xml_session_http && typeof XMLHttpRequest != 'undefined')
{
try
{
xml_session_http = new XMLHttpRequest();
}
catch (e)
{
xml_session_http = false;
}
}
return xml_session_http;
}
var session_http = get_session_HTTPObject();
function init_page_header()
{
window.setInterval( 'checkSessionStatus();', 30000);
}
This seems incredibly long for what it is doing.
I am still learning jquery and am able to do some basic ajax calls like this one, which places a returned value in a div:
$(document).ready(function()
{
$('#users_online').load('/show_users_online.php');
var refreshId = setInterval(function()
{
$('#users_online').load('/show_users_online.php');
}, 2000);
$.ajaxSetup({ cache: false });
});
The issue with the first bit of code is that it returns a value of 'inactive', which is then acted on by the client (window redirect).
Is it possible to do this in Jquery without winding up with dozens of lines of code? I may already know how to do this and am not seeing the forest for the trees -- some guidance here is appreciated.
Even if its very vampiric question style, should look like
$.get('/check_session.php', function( data ) {
if( data === 'inactive' ) {
window.location='/logout.php';
document.getElementById('session_divbox').innerHTML = data;
}
});
I have a Windows app that contains a browser control that loads pages from my website. However, due to the Windows app, I cannot debug Javascript in the usual ways (Firebug, console, alerts, etc).
I was hoping to write a jQuery plug-in to log to an external browser window such that I can simply do something like:
$.log('test');
So far, with the following, I am able to create the window and display the templateContent, but cannot write messages to it:
var consoleWindow;
function getConsoleWindow() {
if (typeof (consoleWindow) === 'undefined') {
consoleWindow = createConsoleWindow();
}
return consoleWindow;
}
function createConsoleWindow() {
var newConsoleWindow = window.open('consoleLog', '', 'status,height=200,width=300');
var templateContent = '<html><head><title>Console</title></head>' +
'<body><h1>Console</h1><div id="console">' +
'<span id="consoleText"></span></div></body></html>';
newConsoleWindow.document.write(templateContent);
newConsoleWindow.document.close();
return newConsoleWindow;
}
function writeToConsole(message) {
var console = getConsoleWindow();
var consoleDoc = console.document.open();
var consoleMessage = document.createElement('span');
consoleMessage.innerHTML = message;
consoleDoc.getElementById('consoleText').appendChild(consoleMessage);
consoleDoc.close();
}
jQuery.log = function (message) {
if (window.console) {
console.log(message);
} else {
writeToConsole(message);
}
};
Currently, getElementById('consoleText') is failing. Is what I'm after possible, and if so, what am I missing?
Try adding
consoleDoc.getElementById('consoleText');
right before
consoleDoc.getElementById('consoleText').appendChild(consoleMessage);
If the line you added is the one that fails, then that means consoleDoc is not right, if the next line is the only one that fails then ..ById('consoleText') is not matching up
If I don't close() the document, it appears to work as I hoped.