Using Android or a desktop browser, please visit this WhatsApp test page and click the Send button. If WhatsApp is not installed it will show you a message.
How does the code detection on that page work? I tried the following but nothing happens.
try {
location.href = 'whatsapp://send/?phone=62812345678&text=test';
} catch (e) {
console.log(e);
}
Looking at the page, it appears that at least on Chrome, they programmatically open an iframe with the src of whatsapp://send/?phone=<number>&text=test. They then start a 1000ms timeout after which the "Looks like you don't have WhatsApp installed!" text is shown. This timeout is cancelled by an blur event handler, meaning that their check is based on your device opening WhatsApp when that URL is loaded, which blurs the window.
The function which triggers after the timeout also seems to check if the timeout took longer than 1250ms. I suspect that this handles the case where your phone's browser stops executing JS timers when it changes apps.
On IE, they use window.navigator.msLaunchUri, which accepts a noHandlerCallback.
See for yourself by opening your browser's devtools and searching for WhatsAppApiOpenUrl. On Chrome, the Search can be found from the devtools' menu:
Here's some example code.
const detectWhatsapp = (phone, text) => {
const uri = `whatsapp://send/?phone=${encodeURIComponent(
phone
)}&text=${encodeURIComponent(text)}`;
const onIE = () => {
return new Promise((resolve) => {
window.navigator.msLaunchUri(
uri,
() => resolve(true),
() => resolve(false)
);
});
};
const notOnIE = () => {
return new Promise((resolve) => {
const a =
document.getElementById("wapp-launcher") || document.createElement("a");
a.id = "wapp-launcher";
a.href = uri;
a.style.display = "none";
document.body.appendChild(a);
const start = Date.now();
const timeoutToken = setTimeout(() => {
if (Date.now() - start > 1250) {
resolve(true);
} else {
resolve(false);
}
}, 1000);
const handleBlur = () => {
clearTimeout(timeoutToken);
resolve(true);
};
window.addEventListener("blur", handleBlur);
a.click();
});
};
return window.navigator.msLaunchUri ? onIE() : notOnIE();
};
Please note that it adds an event listener each time it's called. If you're rolling this out into production, please use window.removeEventListener to remove handleBlur after the promise resolves. It also appends a DOM node into the body, if that matters to you.
Usage example:
detectWhatsapp('<your number here>', 'test').then(hasWhatsapp =>
alert(
'You ' +
(hasWhatsapp ? 'have WhatsApp' : "don't have WhatsApp")
)
)
Here my testing on Android:
Built-in Browser (Webview) and Firefox if WA installed You can use iframe to auto open WhatsApp
Chrome and Opera Need user click action
but luckily I only need this simple code to detect if whatsapp installed
document.querySelector('#openWA').addEventListener('click', function() {
var f = Date.now(),
j = setTimeout(function() {
if (Date.now() - f > 1250)
return;
alert('WA not installed')
}, 1e3);
})
<a href="whatsapp://send/?phone=62812345678&text=test" id="openWA">Send to WhatsApp</button>
<!-- Auto open on WebView and Firefox -->
<iframe id="launcher" src="whatsapp://send/?phone=62812345678&text=test" style="display: none;"></iframe>
If you have jquery, bassed on the code above if whats app does not open open a new page using whatsapp web instead of iframe launcher:
$('a[href^="whatsapp://send?"]').click(function() {
var button = this,
f = Date.now(),
j = setTimeout(function() {
if (Date.now() - f > 1025){
return;
}else{
var newLink = button.getAttribute('href').replace("whatsapp://send?", "https://web.whatsapp.com/send?");
button.setAttribute('href', newLink);
button.setAttribute('target', "_blank");
$(button).closest('div').append('<a class="hide new" href="' + newLink + '" target="_blank" ></a>');
$(button).closest('div').find('a.new')[0].click();
}
}, 1e3);
})
My router.js, which is in public directory works the following way:
First, listens to the event of clicking an 'a' tag
Then, prevents following the link and passes the href value to this function
function loadPage(targetUrl) {
if (targetUrl == "/") {
loadHome(); //Loads Home Page
} else {
if (isSpanish()) {
var direction = "/pages/es" + targetUrl + ".html";
} else {
var direction = "/pages/en" + targetUrl + ".html";
}
var subDirections = direction.split("/");
$('#content').load(direction, function (response, status, xhr) { //Loads content
if (status == "error") {
$("#error-popup").slideDown();
$("#error-popup-wrapper").fadeIn();
document.title = "404" + titleAddon;
} else {
document.title = document.getElementById("title").innerHTML + titleAddon;
window.history.pushState({ url: "" + targetUrl + "" }, null, targetUrl);
}
});
window.scrollTo(0, 0);
}
};
But I believe is conflicting with my index.js which controlls the only route I have:
app.get('*', (req, res) => {
res.sendFile(path.join(__dirname, '/views/index.html'));
});
Everytime I click on a link, I believe the client is requesting the server for the route, and my router.js loads it correctly, but I don't want the page to reload.
How could I solve this?
P.D. Sometimes the page doesn't reload, generally when clicking the menu links. Not sure why.
The website I'm uploading this code to is: https://testing.fsupv2017.webs.upv.es
I have a function I'm using to open PDF's in a new tab of the browser. The user may want to navigate to a different page than the one opened, so page can also be updated by the function:
openpdf: function(url, page, pageCount){
try {
console.log('the page count is ' + pageCount);
var page = new Number(page) + new Number(pageCount);
if (mobileAndTabletcheck()){
console.log('mobile detected');
return window.open(url + '#page' + page, 'somename');
}
console.log('no mobile detected')
return window.open(url + '#page=' + page, 'somename');
}
catch(e){
console.log(e)
}
},
The problem I'm having is that when the user clicks to navigate to the new page of the pdf, the URL is updated with the correct page number, but the viewer stays on the page originally opened.
Does anyone know how to make the current page update when the URL is updated?
You may use the local storage as a location to keep track of the open documents. I believe that the pdf viewer and the main page stays on the same domain. SO you may try something like this.
openpdf: function(url, page, pageCount){
try {
console.log('the page count is ' + pageCount);
var page = new Number(page) + new Number(pageCount);
if (mobileAndTabletcheck()){
console.log('mobile detected');
return window.open(url + '#page' + page, 'somename');
}
console.log('no mobile detected')
return window.open(url + '#page=' + page, 'somename');
}
catch(e){
console.log(e)
}
var openedLinks = JSON.parse(localStorage.getItem("links"));
openedLinks.push("Your URL here");
localStorage.setItem("links", JSON.stringify(names));
}
On the pdf viewer page, just update the local storage.
onpageChanged : function(){
var openedLinks = JSON.parse(localStorage.getItem("links"));
var index = items.indexOf("Your current Url");
if (index !== -1) {
openedLinks[index] = "Your updated URL";
}
localStorage.setItem("links", JSON.stringify(names));
}
And finally on the main page, use something like a timer to keep track of the opened links.
setInterval(function(){
var openedLinks = JSON.parse(localStorage.getItem("links"));
$("#someDiv").html(openedLinks.join(","));
},1000);
Hope this works for you. The code is not tested and may have errors.
Evening All,
I have a Jquery function running from my aspx page (When a button is clicked).
It runs a [webmethod] which if successful returns to the 'OnSuccess' function.
From here I want to navigate the user to: /Project/Invoices/List.aspx
function Onsuccess(CommentSuccessfullyUpdated) {
if (CommentSuccessfullyUpdated == "TRUE") {
window.location = Invoices/List.aspx //My attempt, but unsuccessful
}
else {
alert("Invoice/Details- Error: Removing Invoice.");
}
}
I think its something to do with window.location but this is as far as I have got.....
Any ideas?
Your List.aspx page URL need to be enclosed in quotes, either " " or ' '.
if (CommentSuccessfullyUpdated == "TRUE") {
window.location = 'Invoices/List.aspx';
}
I'm just thinking about the whole site registration process.
A user goes to your site, signs up, and then you tell him you've sent him an email and he needs to verify his email address. So he hits Ctrl+T, pops open a new tab, hits his Gmail fav button, doesn't read a word of your lengthy welcome email, but clicks the first link he sees. Gmail opens your site in yet another tab...
He doesn't need nor want two tabs for your site open, he just wants to view that darn page you've disallowed him access to until he registers.
So what do we do? I saw one site (but I forget what it was) that did a really good job, and it actually refreshed the first tab I had open without me having to press anything.
I'm thinking, it might be nice if we can detect if the user already has a tab to your site open, we could either close the new verification-tab automatically, or tell him he can close it can go back to his other tab (which we've now refreshed and logged him in).
Or, maybe when he got your annoying "please check your email" message, he went directly to his email, replacing your site with his email knowing full well that the email will link him back to the site again. In that case, we don't want to close the tab, but maybe could have saved his location from before, and redirect him there again?
Anyway, that's just the use case... the question still stands. Can we detect if a user already has a tab to your site open?
This question is not about how to detect when a user has completed the sign-up process. Ajax polling or comet can solve that issue. I specifically want to know if the user already has a tab open to your site or not.
I'm fairly late to the party here (over a year), but I couldn't help but notice that you'd missed an incredibly easy and elegant solution (and probably what that website you saw used).
Using JavaScript you can change the name of the window you currently have open through:
window.name = "myWindow";
Then when you send out your confirmation email simply do (assuming you're sending a HTML email):
Verify
Which should result in the verificationLink opening up inside the window your website was already loaded into, if it's already been closed it'll open up a new tab with the window name specified.
You can stop the page functionality when user opened another tab or another window or even another browser
$(window).blur(function(){
// code to stop functioning or close the page
});
You can send an AJAX request every X seconds from the original tab that asks the server if it received a request from the email.
You cannot close the second tab automatically, but you could have it ask the server after 3X seconds whether it heard from the first tab.
What I have here is a little bit different use case to you but it detects if the site is being accessed in another tab. In this case I wanted to limit people using some call center pages to only one tab. It works well and is purely client-side.
// helper function to set cookies
function setCookie(cname, cvalue, seconds) {
var d = new Date();
d.setTime(d.getTime() + (seconds * 1000));
var expires = "expires="+ d.toUTCString();
document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}
// helper function to get a cookie
function getCookie(cname) {
var name = cname + "=";
var decodedCookie = decodeURIComponent(document.cookie);
var ca = decodedCookie.split(';');
for(var i = 0; i < ca.length; i++) {
var c = ca[i];
while (c.charAt(0) == ' ') {
c = c.substring(1);
}
if (c.indexOf(name) == 0) {
return c.substring(name.length, c.length);
}
}
return "";
}
// Do not allow multiple call center tabs
if (~window.location.hash.indexOf('#admin/callcenter')) {
$(window).on('beforeunload onbeforeunload', function(){
document.cookie = 'ic_window_id=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/;';
});
function validateCallCenterTab() {
var win_id_cookie_duration = 10; // in seconds
if (!window.name) {
window.name = Math.random().toString();
}
if (!getCookie('ic_window_id') || window.name === getCookie('ic_window_id')) {
// This means they are using just one tab. Set/clobber the cookie to prolong the tab's validity.
setCookie('ic_window_id', window.name, win_id_cookie_duration);
} else if (getCookie('ic_window_id') !== window.name) {
// this means another browser tab is open, alert them to close the tabs until there is only one remaining
var message = 'You cannot have this website open in multiple tabs. ' +
'Please close them until there is only one remaining. Thanks!';
$('html').html(message);
clearInterval(callCenterInterval);
throw 'Multiple call center tabs error. Program terminating.';
}
}
callCenterInterval = setInterval(validateCallCenterTab, 3000);
}
To flesh out John's answer, here is a working solution that uses plain JS and localStorage and updates the DOM with the count of the currently open tabs. Note that this solution detects the number of open tabs/windows for a given domain within one browser, but does not maintain the count across different browsers.
It uses the storage event to keep the count synchronized across all open tabs/windows without any need for refreshing the page.
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title></title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<meta name="robots" content="noindex, nofollow">
<meta name="googlebot" content="noindex, nofollow">
<meta name="viewport" content="width=device-width, initial-scale=1">
<script>
(function() {
var stor = window.localStorage;
window.addEventListener("load", function(e) {
var openTabs = stor.getItem("openTabs");
if (openTabs) {
openTabs++;
stor.setItem("openTabs", openTabs)
} else {
stor.setItem("openTabs", 1)
}
render();
})
window.addEventListener("unload", function(e) {
e.preventDefault();
var openTabs = stor.getItem("openTabs");
if (openTabs) {
openTabs--;
stor.setItem("openTabs", openTabs)
}
e.returnValue = '';
});
window.addEventListener('storage', function(e) {
render();
})
function render() {
var openTabs = stor.getItem("openTabs");
var tabnum = document.getElementById("tabnum");
var dname = document.getElementById("dname");
tabnum.textContent = openTabs;
dname.textContent = window.location.host
}
}());
</script>
</head>
<body>
<div style="width:100%;height:100%;text-align:center;">
<h1 >You Have<h1>
<h1 id="tabnum">0</h1>
<h1>Tab(s) of <span id="dname"></span> Open</h1>
</div>
</body>
</html>
To add to other answers:
You can also use localStorage. Have an entry like 'openedTabs'. When your page is opened, increase this number. When user leaves the page, decrease it.
The user will still have a session at the server. Why not store the user's location prior to registration, and when they confirm their registration, read the location back out of the session and redirect back to that page. No tab magic required. It's certainly not what I'd expect from a signup process.
It is possible to track number of tabs of your site opened by saving data in localstorage of each tab and counting the same, I created a github repository which can track number of tabs of your website a user has opened.
To use it Include tab-counter.js in your page and it will start tracking number of opened tabs.
console.log(tabCount.tabsCount());
Here's a system that uses broadcast channels for cross tab comms. It also assigns a unique ID per tab and manages the discovery of already opened tabs, for new tabs. Finally, using the ID as a stable index, it allows the user to rename their tabs. Tab closing events are handled via polling as well (unload events are unreliable).
This plugs into redux via the callbacks in the constructor. These are onNewTab, onDestroyTab, onRenameTab in this example.
import { setTabs } from './redux/commonSlice';
import { store } from './redux/store';
const promiseTimeout = (ms, promise) => {
let id;
let timeout = new Promise((resolve, reject) => {
id = setTimeout(() => {
reject('Timed out in ' + ms + 'ms.');
}, ms)
})
return Promise.race([
promise,
timeout
]).then((result) => {
clearTimeout(id);
return result;
})
};
// Promise that can be resolved/rejected outside of its constructor. Like a signal an async event has occured.
class DeferredPromise {
constructor() {
this._promise = new Promise((resolve, reject) => {
// assign the resolve and reject functions to `this`
// making them usable on the class instance
this.resolve = resolve;
this.reject = reject;
});
// bind `then` and `catch` to implement the same interface as Promise
this.then = this._promise.then.bind(this._promise);
this.catch = this._promise.catch.bind(this._promise);
this.finally = this._promise.finally.bind(this._promise);
this[Symbol.toStringTag] = 'Promise';
}
}
class TabManager {
tabCreateCallback = undefined;
tabDestroyCallback = undefined;
tabRenameCallback = undefined;
constructor(onNewTab, onDestroyTab, onRenameTab) {
this.tabCreateCallback = onNewTab.bind(this);
this.tabDestroyCallback = onDestroyTab.bind(this);
this.tabRenameCallback = onRenameTab.bind(this);
// creation time gives us a total ordering of open tabs, also acts as a tab ID
this.creationEpoch = Date.now();
this.channel = new BroadcastChannel("TabManager");
this.channel.onmessage = this.onMessage.bind(this);
// our current tab (self) counts too
this.tabs = [];
this.tabNames = {};
// start heartbeats. We check liveness like this as there is _no_ stable browser API for tab close.
// onbeforeunload is not reliable in all situations.
this.heartbeatPromises = {};
this.heartbeatIntervalMs = 1000;
setTimeout(this.doHeartbeat.bind(this), this.heartbeatIntervalMs);
}
doComputeNames() {
for (let i = 0; i < this.tabs.length; i++) {
const tab = this.tabs[i];
const name = this.tabNames[tab];
const defaultName = `Tab ${i + 1}`;
if (!name) {
this.tabNames[tab] = defaultName;
if (this.tabRenameCallback) {
this.tabRenameCallback(tab, name);
}
// if it's a default pattern but wrong inde value, rename it
} else if (name && this.isDefaultName(name) && name !== defaultName) {
this.tabNames[tab] = defaultName;
if (this.tabRenameCallback) {
this.tabRenameCallback(tab, name);
}
}
}
}
doHeartbeat() {
for (let tab of this.tabs) {
if (tab === this.creationEpoch) {
continue;
}
this.channel.postMessage({ type: "heartbeat_request", value: tab });
const heartbeatReply = new DeferredPromise();
heartbeatReply.catch(e => { });
// use only a fraction of poll interval to ensure timeouts occur before poll. Prevents spiral of death.
let heartbeatReplyWithTimeout = promiseTimeout(this.heartbeatIntervalMs / 3, heartbeatReply);
// destroy tab if heartbeat times out
heartbeatReplyWithTimeout.then(success => {
delete this.heartbeatPromises[tab];
}).catch(error => {
delete this.heartbeatPromises[tab];
this.tabs = this.tabs.filter(id => id !== tab);
this.tabs.sort();
this.doComputeNames();
if (this.tabDestroyCallback) {
this.tabDestroyCallback(tab);
}
});
this.heartbeatPromises[tab] = heartbeatReply;
}
// re-schedule to loop again
setTimeout(this.doHeartbeat.bind(this), this.heartbeatIntervalMs);
}
doInitialize() {
this.tabs = [this.creationEpoch];
this.doComputeNames();
if (this.tabCreateCallback) {
this.tabCreateCallback(this.creationEpoch);
}
this.channel.postMessage({ type: "creation", value: this.creationEpoch });
}
onMessage(event) {
if (event.data.type == "creation") {
const newTabId = event.data.value;
// add the new tab
if (!this.tabs.includes(newTabId)) {
this.tabs.push(newTabId);
this.tabs.sort();
this.doComputeNames();
if (this.tabCreateCallback) {
this.tabCreateCallback(newTabId);
}
}
// send all of the tabs we know about to it
this.channel.postMessage({ type: "syncnew", value: this.tabs });
// those tabs we just sent might already have custom names, lets send the older rename requests
// which would have had to have occured. I.E. lets replay forward time and sync the states of ours to theirs.
for (let tab of this.tabs) {
const name = this.tabNames[tab];
if (name && !this.isDefaultName(name)) {
this.notifyTabRename(tab, name);
}
}
} else if (event.data.type == "syncnew") {
let newTabs = [];
// just got a list of new tabs add them if we down't know about them
for (let id of event.data.value) {
if (!this.tabs.includes(id)) {
newTabs.push(id);
}
}
// merge the lists and notify of only newly discovered
if (newTabs.length) {
this.tabs = this.tabs.concat(newTabs);
this.tabs.sort();
this.doComputeNames();
for (let id of newTabs) {
if (this.tabCreateCallback) {
this.tabCreateCallback(id);
}
}
}
} else if (event.data.type == "heartbeat_request") {
// it's for us, say hi back
if (event.data.value === this.creationEpoch) {
this.channel.postMessage({ type: "heartbeat_reply", value: this.creationEpoch });
}
} else if (event.data.type == "heartbeat_reply") {
// got a reply, cool resolve the heartbeat
if (this.heartbeatPromises[event.data.value]) {
// try catch since this is racy, entry may have timed out after this check passed
try {
this.heartbeatPromises[event.data.value].resolve();
} catch {
}
}
} else if (event.data.type == "rename") {
// someone renamed themselves, lets update our record
const { id, name } = event.data.value;
if (this.tabs.includes(id)) {
this.tabNames[id] = name;
// first original (potentially illegal) rename callback first
if (this.tabRenameCallback) {
this.tabRenameCallback(id, name);
}
// force tab numbers back to consistent
this.doComputeNames();
}
}
}
setTabName(id, name) {
if (this.tabs.includes(id)) {
this.tabNames[id] = name;
this.notifyTabRename(id, name);
if (this.tabRenameCallback) {
this.tabRenameCallback(id, name);
}
// force tab numbers back to consistent
this.doComputeNames();
}
}
notifyTabRename(id, name) {
this.channel.postMessage({ type: "rename", value: { id, name } });
}
isDefaultName(name) {
return name.match(/Tab [0-9]+/)
}
getMyTabId() {
return this.creationEpoch;
}
getMyTabIndex() {
return this.tabs.findIndex(tab => tab === this.creationEpoch);
}
isMyTab(id) {
return id === this.creationEpoch;
}
getAllTabs() {
return this.tabs.map((tab, idx) => {
return { id: tab, index: idx, name: this.tabNames[tab] ?? "" };
}, this);
}
}
function onDestroyTab(id) {
store.dispatch(setTabs(this.getAllTabs()));
console.log(`Tab ${id} destroyed`);
}
function onNewTab(id) {
store.dispatch(setTabs(this.getAllTabs()));
console.log(`Tab ${id} created`);
}
function onRenameTab(id, name) {
store.dispatch(setTabs(this.getAllTabs()));
console.log(`Tab ${id} renamed to ${name}`);
}
const TabManager = new TabManager(onNewTab, onDestroyTab, onRenameTab);
export default TabManager;
Initialize it on page load
window.addEventListener("DOMContentLoaded", function (event) {
TabManager.doInitialize();
});
Access any of the methods on the static object at any time. Note that you can get rename events out of order from create / destroy. This could be resolved, but it wasn't important for me.