using if else statements with a timer - javascript

Im trying to set up a series of if else statements using a timer. Ideally, these if else statements would display images according to real time. However, if there is a way to set up my own timer and have the images display using if else statements that would also work. Here's what I'm thinking;
if (time < 7:00) {
document.getElementById("whatever").style.display="block";
}
Please assist if anyone knows the best possible solution for this particular problem. THANK YOU!!

If you just want a condition that becomes truthy when it's earlier than 7pm:
if (new Date().getHours() < 19) { }
The getHours() method returns the hour of the day between 0 and 23.
In a timer function it would look like this:
function doMagicStuff()
{
var now = new Date();
if (now.getHours() < 19) {
}
// other conditions based on time
}
// let it run approximately every second; doesn't have to be very accurate
setInterval(doMagicStuff, 1000);

Related

Working on my own Javascript countdown timer/ Pomodoro technique

Since I have been teaching myself how to code in JavaScript by watching tutorials on YouTube and reading Head First Javascript book, I decided to set my own challenge by building something that has been quite effective to me - The Pomodoro technique! I have been using this technique since I have started learning JavaScript. And whilst I was thinking of a JavaScript coding challenge that involves arrays, functions, DOM, etc. I thought why not the Pomodoro technique that can have an array of activities to do during my 5-minute break, a function for the 25 and 5-minute timer and then style it using HTML and CSS. Anyway, here is my code so far...
<script>
function startTimer() {
var timer = document.getElementById("myTimer").innerHTML;
var arr = timer.split(":");
var hour = arr[0];
var min = arr[1];
var sec = arr[2];
if (sec == 0) {
if (min == 0) {
if (hour == 0) {
alert(pushup());
window.location.reload();
return;
}
hour--;
min = 60;
if (hour < 10) hour = "0" + hour;
}
min--;
if (min < 10) min = "0" + min;
sec = 59;
}
else sec--;
if (sec < 10) sec = "0" + sec;
document.getElementById("myTimer").innerHTML = hour + ":" + min + ":" + sec;
setTimeout(startTimer, 1000);
function pushup() {
var minBreak = ["Do 5 push ups!", "Do 10 push ups!", "Do 15 push ups!",
"Do 5 sit ups!", "Do 10 sit ups!", "Do 15 sit ups!",
"Clean room!", "Do laundry!", "Walk dog!" ];
var rand1 = Math.floor(Math.random() * minBreak.length);
var phrase = minBreak[rand1];
alert(phrase)
};
};
</script>
</head>
<body onload="startTimer();">
<p id="myTimer">00:00:10</p>
</body>
I did this step by step creating the pushup function first, which was easy to do, setting alerts on each step so I knew I was going on the right track too. However, startTime function is a copy on a YouTube video. As much as I would have loved to figure this out myself I was struggling hard to set a timer in the browser! The only successful way I can do was use the setInterval method. However, the video was only one minute long and it does not explain how it works. I made sure I gone through line to line to understand how it works, the .split method, why multiple of if statements, etc. Wrote notes down and make sure I understood. Now, when the timer goes off at 10 secs it alerts one of the minBreak chores in random, success! BUT then shows another alert saying "The page says undefined" why is this? And (because I am new to creating this) how would you have written this code? I am thinking to have multiple variables of different chores. So, var pushup will have an array of 1 push up, 2 push up and so on. var situp will have an array of 1 situp, 2 situp and so on. What statements or methods should I use so the math.random can pick one of many different variables arrays randomly instead of being all in one. Not really asking for you to show me a code of how it's done but a route of using for statements, or while, or ifs, etc. sorry if doesn't make sense.. I am new to this! But just trying to make something up on the way and challenge myself, and question myself. but at the same time need a mentor/ teacher to show me the way.
You are getting the undefined message, because you have twice an alert. The second one uses a function return value to display, but that function does not return anything, hence undefined:
alert(pushup());
So the function pushup performs itself an alert, which is like you want it. But then the function returns to the above statement, where the function's result is displayed in an alert. It is undefined.
So you can fix this by just calling the function:
pushup();
As far as I understand this was the only issue to be fixed.

comparing time not working javascript

I am trying to compare the time now and a time in a future date. When these times are the same I want to show a message. However, the code below is not working. I have been checking the console and now.getTime() is never the same as end.getTime(), presumably as they are in ms?
Does anyone know how to overcome this? Following this answer here I believe it should work.
function compareTimes() {
var end = new Date("August 31, 2016 11:04:18");
var now = new Date();
if (now.getTime() == end.getTime()) {
clearInterval(timer);
document.getElementById('countup').innerHTML = 'EXPIRED!';
return;
}
}
setInterval(compareTimes, 1000);
setInterval will execute the function compareTimes every second and your function will compare the times at that very instant. It is highly unlikely that both the times will be same, hence you won't be able to set your div to EXPIRED . In order to overcome this i suggest you check if the time is greater than the current time i.e if (now.getTime() > end.getTime()) then set the state as EXPIRED in your div.

Decrement a variable once a day - Javascript

I'm trying to decrement a variable once a day. I have written the following code for that.
var counter = 10; //any value
setInterval(function() {
counter = counter - 1;
}, 86400000);
Is there a better or efficient way to achieve the same thing ?
P.S : - I do not wish to use any libraries.
The only thing I see you miss is to set the initial value of counter variable.
I would write:
var counter = 1000; // or any useful value
setInterval(function() {
--counter;
}, 24 * 60 * 60 * 1000); // this is more self-explanatory than 86400000, and, being evaluated just once, it will have a tiny effect on the performace of the script
I don't see any problem in the way you write it. You use interval, ok, but this is not the worst evil you may do to set up the variable value.
You may think of another solution with a function which returns you the current counter.
var initialValue = 20000;
function getCounter() {
return initialValue - Math.floor(Date.now() / 1000 / 60 / 60 / 24);
}
console.log(getCounter());
The difference is that it takes the current day number starting from the UNIX time beginning. Every day the day number will be increased, so the result of the function will be decreased by 1.
But still I don't see how this solution can be better than yours.
I'm not totally sure why, but using setInterval like this makes me uncomfortable.
If I were to require this, I would use something like this approach:
var counter = 10;
var timeout = new Date();
setInterval(function(){
if(new Date() >= timeout)
{
--counter; // the action to perform
timeout = new Date(timeout.getTime() + 86400000); // update the timeout to the next time you want the action performed
}
console.log(counter);
},1000); // every second is probably way more frequent than necessary for this scenario but I think is a decent default in general
One thing that this allows is to, for example, set the next timeout to midnight of tomorrow rather than being locked in to "X seconds since the previous execution". The key is the inversion of control - the action itself can now dictate when it should next run.
Though I would probably abstract away the details behind an interface accepting a start, interval, and action.
The biggest problem in my eyes is that you have to keep this one JS process running consistently for days at a time to have it do what you need. The world is not so perfect that things don't need an occasional reboot...including the average JS process.
Personally I would store a timestamp of my starting point, then (whenever I need to know how much time has elapsed) grab a new timestamp and use it to calculate how many days it has been. That way even if something interrupts my process I can still be right where I started.
Maybe use window.localStorage to save the last time, and if it is greater than 60*60*24 (seconds in a day) set the last time to this morning/now/1:00 and then decrease the value and save it.
Example:
var d = new Date();
var mins = -(1+d.getHours())*60+d.getMinutes();
var secs = mins*60+d.getSeconds(); // total seconds passed today from 1:00
var now = d.getCurrentTime():
var lastCheck = localStorage.getItem("lastCheck");
if (!lastCheck)
{
localStorage.saveItem("lastCheck",now-secs); // beginning of today
}
var dayPassed = now - lastCheck > 24*60*60; // change to see if a day has passed
if (dayPassed)
{
// save seconds
localStorage.setItem("counter",localStorage.getItem("counter")-1);
localStorage.saveItem("lastCheck",now-secs); // beginning of today
}
It makes more sense to me to check how many days have passed since a specific date and decrement that number of days from the counter. Mostly just because I wouldn't expect anybody to leave the same page open without the need or want to reload for days on end. I would do something like this:
counter = 365; // original counter
var start = new Date(2016, 03, 20); // original date
var now = new Date();
var days = Math.floor(Math.abs(start.getTime()-now.getTime())/(24*60*60*1000))
counter -= days;
That way every time you visited the page, it would be decremented correctly. Note that this ignores any issues with leap days or time zones. The example above would have a counter of 360 for me. And then if you did expect it to be open for days, reload it automatically with:
self.setTimeout(function(){document.location.reload()}, 86400000);

Run code once a day

I was just wondering if it is possible to have a javascript for loop that only iterates through the loop once a day i.e. when the date changes?
for(i=0; i < myArray.length; i++){
alert(myArray[i]);
}
So in the above loop, let it run, and freeze it or something only till the data changes, and the do another iteration, and just keep on doing that.. You know what I mean.
Thanks in advance!
Using localStorage is the best way to go when you don't have a server (because a user can change the computer's time and break your logic, and using a server it's harder to hack this)
Method below is more bulletproof:
// checks if one day has passed.
function hasOneDayPassed()
// get today's date. eg: "7/37/2007"
var date = new Date().toLocaleDateString();
// if there's a date in localstorage and it's equal to the above:
// inferring a day has yet to pass since both dates are equal.
if( localStorage.yourapp_date == date )
return false;
// this portion of logic occurs when a day has passed
localStorage.yourapp_date = date;
return true;
}
// some function which should run once a day
function runOncePerDay(){
if( !hasOneDayPassed() ) return false;
// your code below
alert('Good morning!');
}
runOncePerDay(); // run the code
runOncePerDay(); // does not run the code
If you want something to happen at predefined intervals, you can set a timeout/interval:
http://www.w3schools.com/js/js_timing.asp
For example:
var dayInMilliseconds = 1000 * 60 * 60 * 24;
setInterval(function() { alert("foo"); },dayInMilliseconds );
edit: since you mentioned that the code will be running in a browser, this assumes the browser is running for at least 24 hrs and will not work otherwise.
the best way to achieve it is by creating a cookie that lasts for1 day..
Even if after the refresh of the web page or browser gets closed that countdown will still continue..
setcookie($cookie_name, $cookie_value, time() + 86400, "/");
This means 86400 = 1 day
Hope it helps

ajax/JS timed countdown?

Let me explain what I'm trying to do.
I want to make a simple box which counts down numbers at intervals I specify.
For example, I'd like to set it to start at 150, and then I want to set it to drop by 15 every 30 seconds.
Is this possible with AJAX/Javascript? If so, could someone point me in the right direction?
Would really appreciate any help on this script, been Googling for hours now! :(
Cheers
Kieran
Have a look at the setTimeout or setInterval methods, they allow you to execute a function after a specified number of milliseconds (1000ms = 1second). Use that, to call a function that keeps dropping the number and writes it to a HTML element to the user can see it.
this isn't tested, but i hope it shows you the way to go.
var start = 150;
var drop = 15;
var interval = 30;
function countdown(){
document.getElementById('mybox').innerHTML = start;
start-=drop;
window.setTimeout("countdown",interval*1000);
}
countdown();
You may use jQuery to do that, see http://keith-wood.name/countdown.html -> tab Callbacks
Keep in mind that 30 seconds in my browser are not necessarily equal to 30 seconds in your browser. It depends on the workload of the browser.
The time difference is minor for a short time but can increase over a long time. The times will drift apart. If the times must not be equal (or nearly equal) between two visitors than such simple solution should be fine.
We had once a problem to introduce a live clock / countdown in one of our projects. We build a script with javascript, ajax and PHP for clock synchronisation (server time was timeserver).
You should use setInterval / clearInterval which is made for this kind of tasks:
function cooldown(element, start, stop, step, delay) {
var current = start;
element.innerHTML = current;
var timer = setInterval(function () {
current -= step;
if(current < stop) current=stop;
element.innerHTML = current;
if(current == stop) clearInterval(timer);
}, delay*1000);
}
Demonstrated here : http://jsfiddle.net/PCMHn/

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