Develop Reference

Redirecting automatically after Devise log-out with Javascript?

I'm using Devise, and automatic logout works great.
However, the user is not informed they have been logged out until they make another request, at which point they are redirected to the sign in page. For AJAX functionality, this is not great, it either fails silently or raises an exception.
Devise wiki doesnt seem to have an example, is there a standard solution to this? A javascript popup with a countdown timer, that does a redirect if the user doesnt click "keep me logged in"?

I ended up implementing jscript timeout something similar to below.
Some unanswered questions:
what happens on switching to another tab?
works in IE?
application.js
//= require timer
// redirect user after 15 minutes of inactivity - should match Devise.timeout_in + 1 second grace period
$(function() {
var logout_timer = new Timer(901, 'users/sign_in', window);
logout_timer.start();
// restart timer if activity
$(document).on('keyup keypress blur change mousemove',function(){
logout_timer.start();
});
});
timer.js
Timer = function(time_in_secs, path, windowobj) { // window object must be injected, else location replace will fail specs
var self = this; // 'this' not avail in setInterval, must set to local var avail to all functions
this.state = 'init'
this.time_remaining = time_in_secs;
this.timer_id = undefined;
this.start = function() {
// if restarting, there will be a timer id. Clear it to prevent creating a new timer, reset time remaining
if (this.timer_id !== undefined) {
this.time_remaining = time_in_secs;
this.clear_timer(this.timer_id, self);
}
this.state = 'running';
this.timer_id = setInterval(function() { // IE any version does not allow args to setInterval. Therefore, local variables or refer to self obj
self.time_remaining -= 1;
// log status every 10 seconds
if ((self.time_remaining % 10) === 0) {
console.log("logging user out in " + self.time_remaining + " seconds");
}
// when timer runs out, clear timer and redirect
if ( self.time_remaining <= 0 ) {
self.clear_timer(self.timer_id, self);
self.do_redirect(path, windowobj);
};
}, 1000);
return this.timer_id;
};
this.clear_timer = function(timer_id, self) {
self.state = 'stopped';
clearInterval(self.timer_id);
}
this.remaining = function() {
return this.time_remaining;
};
this.do_redirect = function(path, windowobj) {
console.log("Redirecting to " + path);
self.state = 'redirecting';
windowobj.location = path;
}
}

Gmail-like countdown timer not working

I've been trying to recreate a countdown timer similar to the one gmail uses that when you get disconnected from internet. The ajax request fails then it begin a short countdown then makes another ajax request and if it fails again then begin a longer countdown and so forth. Once a determined countdown value is reached (lets say 1 minute), the countdown is maintained at 1 minute until the internet connection is recovered or the servers comes back.
I don't want to use a plugin because this code will be embedded in a micro-controller that has limited space and also prefer not to place it as external file for practical reasons, even though jQuery library will already be external.
Everything should trigger onload, and continue automatically (i.e. no control inputs will be used).
So far I've developed code that does what I want if the ajax request succeeds or fails immediately but if there is a latency on the ajax request status (as for example having the server down) the browser won't produce an immediate result and my code fails.
I know what I stated above because I actually took the server down and was been help by firebug on Mozilla Firefox to see that the ajax result (success or failure) wasn't triggered immediately but keep waiting for several seconds.
Help please!
html code:
<div id='tempFail' ></div>
jQuery code:
$(document).ready(function()
{
//do when DOM ready - http://api.jquery.com/ready/
var timerSpeed = [1000, 5000, 10000, 20000, 30000, 60000];
// current time in ms since 1/1/1970, plus the initial reload interval
var end = (new Date).getTime() + timerSpeed[1];
var n=0;
var m=0;
setInterval(function()
{
var now = (new Date).getTime();
// Current time left to re-load in seconds, sometimes it goes to negative values, see below
var secLeft = Math.floor(( end - now ) / 1000);
// if secLeft is negative multiply by zero...equal to secLeft=0, this will produce an error of one second approximately
var timeToload = (secLeft < 0) ? secLeft * 0 : secLeft;
if (n!=0)
{
//check for failed or delayed request\n\
$('#tempFail').html('Failed or delayed response. Will auto load in: '+timeToload+ ' seconds!');
}
if( (secLeft)<=0)// if reload time is reached do
{
if (m==0)//used to prevent multiple continue reloads when ajax request status is not yet defined
{
m=1;
$.getScript('script_vars.js').done(function (data)
{
//if request succeeded
m=0;
n = 0;
end = (new Date).getTime() + timerSpeed[1];
// Time to load after the initial interval set above
$('#tempFail').html('');
//other code on success here
})
.fail(function()
{
//if request failed
m=0;
n ++;
if(n==6) n=5;
switch(n){ //timer delay for failed request\n\
case 1:
end = (new Date).getTime() + timerSpeed[1];
break;
case 2:
end = (new Date).getTime() + timerSpeed[2];
break;
case 3:
end = (new Date).getTime() + timerSpeed[3];
break;
case 4:
end = (new Date).getTime() + timerSpeed[4];
break;
case 5:
end = (new Date).getTime() + timerSpeed[5];
break;
}
});
}
}
}, 1000);
});

You asked for an example so I've written the following, you may want to wrap the contents of the function within another function so you can repeat it/don't have to worry about namespaces/etc. Didn't test so don't expect bug free!
Using window.setTimeout for every action, separated each stage into it's own function so code paths can more easily be followed.
$(document).ready(function () { // http://api.jquery.com/ready/
var $tempFail = $('#tempFail'),
delay = [1000, 5000, 10000, 20000, 30000, 60000],
delay_index = 0,
delay_ends = 0,
inform_user_ref = null,
inform_user = function inform_user() {
var now = (new Date).getTime(),
delta; // for difference, calculate later
if (delay_ends > now) { // if we're waiting for a retry
delta = Math.floor((delay_ends - now ) / 1000); // calculate time to wait
$tempFail.html('Failed or delayed response. Will auto load in: '+delta+ ' seconds!'); // let people know
window.setTimeout(inform_user, 200); // loop countdown timer
// can fast refresh this as it's just a countdown
}
},
get_success = function () {
$tempFail.html('');
// .. code on success
},
get_fail = function () {
delay_index < 5 && ++delay_index; // increment delay_index
get_initialise(); // retry
window.clearTimeout(inform_user_ref); // remove any old countdown timer
inform_user_ref = inform_user(); // and display new countdown
},
get_try = function () {
$.getScript('script_vars.js')
.done(get_success)
.fail(get_fail);
},
get_initialise = function () {
delay_ends = (new Date).getTime() + delay[delay_index];
window.setTimeout(get_try, delay[delay_index]); // retry
};
get_initialise(); // initial
});

Wow! Mr Paul S. your code was crazy good. I just made a couple of adjustments to have it perfectly working as I need it.
Added the following on ajax success:
delay_index = 0; //reset delay_index
get_initialise(); // retry
so I keep the code running every 5 seconds if everything goes ok.
2.
Added two new variables: let_cntDwn_end and ajax_rqst_status to avoid countdown number jumping (to let countdown finish before beginning the next one ) and to display a message while the ajax request haven't given any result respectively.
Here is the new code:
$(document).ready(function(){ //do when DOM ready - http://api.jquery.com/ready/
var $tempFail = $('#tempFail'),
delay = [5000, 5000, 10000, 20000, 30000, 60000],
delay_index = 0,
delay_ends = 0,
inform_user_ref = null,
let_cntDwn_end = 0,
ajax_rqst_status = 0, //ajax success or failure triggered
inform_user = function inform_user() {
var now = (new Date).getTime(),
delta; // for difference, calculated later
if (delay_ends > now) { // if we're waiting for a retry
let_cntDwn_end = 1;
delta = Math.floor((delay_ends - now ) / 1000); // calculate time to wait
if (ajax_rqst_status==0){
$tempFail.html('Failed response. Will auto load in: '+delta+ ' seconds!'); // let people know
window.setTimeout(inform_user, 900); // loop countdown timer
// can fast refresh this as it's just a countdown
}
}
else {let_cntDwn_end = 0; get_try();}
},
get_success = function () {
ajax_rqst_status =0;
$tempFail.html('');
// .. code on success
delay_index = 0; //reset delay_index
get_initialise(); // retry
},
get_fail = function () {
ajax_rqst_status =0;
delay_index < 5 && ++delay_index; // increment delay_index
get_initialise(); // retry
window.clearTimeout(inform_user_ref); // remove any old countdown timer
inform_user_ref = inform_user(); // and display new countdown
},
get_try = function () {
if (let_cntDwn_end == 0){
ajax_rqst_status=1;
$tempFail.html('Waiting for Ajax request success or failure'); // let people know
$.getScript('script_vars.js')
.done(get_success)
.fail(get_fail);
}
},
get_initialise = function () {
delay_ends = (new Date).getTime() + delay[delay_index];
window.setTimeout(get_try, delay[delay_index]); // retry
};
get_initialise(); // initial
});

There's also JS lib which handles this for you by monitoring ajax requests.
https://github.com/HubSpot/offline

Facebook server time in javascript

Im trying to show on my site changeable clock synchronized with facebook server.
The fb server time is available at:
https://api.facebook.com/method/fql.query?query=SELECT+now%28%29+FROM+link_stat+WHERE+url+%3D+%271.2%27&format=json
How to make it changeable every second without refreshing the page?

Assuming some non-written functions, it should look like that:
var requestBegin = Date.now();
getServertimeFromFacebook(function callback(fbTime) {
var requestEnd = Date.now();
var latency = (requestEnd - requestBegin) / 2;
var curDevicetime = Date.now(); // = requestEnd, of course
var difference = fbTime - latency - curDeviceTime;
function clock() {
var cur = Date.now();
var curFbTime = cur + difference;
show(curFbTime); // print, log, whatever
};
setInterval(clock, …); // you could use a self-adjusting clock
// by using a setTimeout for each tick
});
You could do
show = function(t) { console.log(new Date(t).toString()); };
getServertimeFromFacebook = function(cb) {
ajax("https://api.facebook.com/method/fql.query?query=SELECT+now%28%29+FROM+link_stat+WHERE+url+%3D+%271.2%27&format=json", function(responsetext) {
var obj = JSON.parse(responsetext);
var ts = obj[0].anon,
tms = ts * 1000;
cb(tms);
});
};

I wouldn't call the API every second.
Instead, I would get the Facebook server time only one time at the beginning. And then, I would increment my time value every second by looping using javascript :
setTimeout(function() { /* increment time */ }, 1000);
Bergi: [{"anon":1354654854}] is a unix time. Indeed, Facebook often (always?) deals with time using this representation.

Rate limiting to prevent malicious behavior in ExpressJS

Someone made me aware of some flaws in an application I'm working on (mostly within my JavaScript on the front-end), that leaves open the possibility of, say, clicking a ton of buttons at once and sending out a ton of transactional emails. This is clearly not good.
I think one way to handle this in ExpressJS is by using app.all() to count the number of requests that happen within a certain timeframe. I'd store this in the session metadata with timestamps, and if more than X requests happen in Y time, I cut them off for awhile until the limit expires.
Has anyone done this before or have any tips/hints to help me out? Something that's easy to drop in and out of my app is preferable. Thanks!

You could use the Collate object in your webpage.
function Collate(timeout) {
this.timeout = timeout || 1000;
}
Collate.prototype = {
time: 0,
idle: function() {
var t = new Date().getTime();
return (t - this.time > this.timeout && (this.time = t));
},
prefer: function(func) {
this.func = func;
clearTimeout(this.timer);
this.timer = setTimeout(func, this.timeout);
}
};
If you want a function to run once and not run again within the next 1 second.
Like if you want to prevent the user from submitting a form many times, you do this:
var timer = new Collate(3000); //3 seconds
button1.onclick = function() {
if(timer.idle()) {
button1.form.submit();
} else alert("Don't click too quickly!");
}
//or on the form tag
<script>var submitTimer = new Collate(3000);</script>
<form action="post" onsubmit="return submitTimer.idle();">
If you expect an event to fire multiple times and only want to react to the last time it fires.
Like if you want to search after a user has finished typing, you do this:
var timer = new Collate(700); //0.7 seconds
textfield1.onkeyup = function() {
timer.prefer(function() {
autocomplete.search(textfield1.value);
});
};

setInterval pauses in Android Browser / Mobile Safari when screen times out

I've built a simple JavaScript-based timer for a mobile webapp; for the sake of example:
var a = 0;
setInterval(function() {
console.log('a', a);
a++;
}, 1000);
This runs just fine in both Mobile Safari and Android Browser. It will log to console every second and increment the value of a accordingly. (Okay, Android Browser doesn't have console.log support, but let's assume it does.)
The issue: if the screen times out (i.e. user stopped interacting with the page), the setInterval function pauses. It resumes when the user turns on their screen again. This won't work for me as I need timer to keep running.
The questions: Is there a way to prevent the setInterval function from pausing when the screen times out? If not, is it possible to prevent the screen from timing out? Any other alternatives?
Thanks in advance!

Basically, no. The phone enters a sleep state to save battery when the screen times out. Since you can't see anything anyway, a large number of processing tasks are stopped. Similar things will occur when you change tabs/windows (the page is unloaded from memory). Right now there is no way to request that the device stays on from a web application. Future support in Android for accessing hardware may provide this functionality, but personally I doubt it.
If you need always running support, you'll need to write native applications for both systems (plus on Android it can always run).

You can use the Page Visibility API to detect when the page is hidden or visible. For example, if the user navigates away from the browser and back again or the screen turns off and on.
I used this answer to help create by solution.
You will need to store the time you set your interval. Then when the visibilityChange event listener indicates the document is visible again, you can calculate the amount of time that has passed since you first started the interval and update your data as needed.
In my case I was creating a count down timer in my Angular2 project. My page was running on an iPad and the timer was pausing whenever the screen turned off. So I added the event listener in my ngOnInit(). Then when the screen turned back on I could update my timer to show the correct time left since it was started.
I am using the moment npm package to handle my date time.
The timerInfo object is a class variable that gets updated by the interval callback. self.zone.run() is used to propagate the changes to the DOM so that the updated time gets displayed.
Written in typescript:
private timerInfo:{
days?:number,
hours?:number,
minutes:number,
seconds:number
};
private startTime:Moment = moment();
private timerDuration:number = 20; // in minutes
private timerHandle:any;
ngOnInit() {
this.setVisibilityListener();
}
private setVisibilityListener():void {
var self = this;
var hidden, visibilityState, visibilityChange;
if (typeof document.hidden !== "undefined") {
hidden = "hidden";
visibilityChange = "visibilitychange";
visibilityState = "visibilityState";
}
var document_hidden = document[hidden];
document.addEventListener(visibilityChange, function () {
if (document_hidden != document[hidden]) {
if (document[hidden]) {
// Document hidden
console.log("document hidden");
} else {
// Document shown
console.log("document shown; setCountDownTimer()");
self.setCountDownTimer();
}
document_hidden = document[hidden];
}
});
}
private setCountDownTimer():void {
var self = this;
if (self.startTime) {
var startMoment = moment(self.startTime);
var endMoment = startMoment.add(self.timerDuration, "minutes");
console.log("endMoment: ", endMoment.toISOString());
self.clearTimer();
var eventTime = endMoment.unix();
var currentTime = moment().unix();
var diffTime = eventTime - currentTime;
var duration = moment.duration(diffTime * 1000, 'milliseconds');
var interval = 1000;
// if time to countdown
if (diffTime > 0) {
self.timerHandle = setInterval(() => {
self.zone.run(() => {
var diff = duration.asMilliseconds() - interval;
if (diff < 0) {
self.clearTimer();
self.timerComplete();
} else {
duration = moment.duration(duration.asMilliseconds() - interval, 'milliseconds');
self.timerInfo = {
days: moment.duration(duration).days(),
hours: moment.duration(duration).hours(),
minutes: moment.duration(duration).minutes(),
seconds: moment.duration(duration).seconds()
};
// console.log("timerInfo: ", JSON.stringify(self.timerInfo));
}
});
}, 1000);
} else {
self.timerComplete();
}
}
}
private clearTimer():void {
if (this.timerHandle) {
clearInterval(this.timerHandle);
this.timerHandle = null;
}
}