Javascript adding variable twice

Question

I have the following code:

var m = 0;
function addmoney(){
    var today = new Date();
    var s =today.getSeconds();
    if(s == 30){
        m += 10;
    }
    document.getElementById('mon').innerHTML=s+" money: "+m;
    t=setTimeout(function(){addmoney()},500);
}

Basically what I'm doing is to add 10 to the value of m every 30 seconds. The problem here is that the variable was actually being added twice. I was wondering why this was the case?

EDIT: Sorry did not mean to do s++, eitherways it did not change much.

FYI, setTimeout(function(){addmoney()},500) is simpler written as setTimeout(addmoney,500) — Felix Kling
– Felix Kling, Commented Dec 2, 2013 at 8:46
You set your timeout function to call after 0.5 seconds. getSeconds() only returns full seconds. So if you call the function at e.g. 12:30:01 100ms which returns 30sec and the next call resolves fast enough the next date could be 12:30:01 700ms which also returns 30sec m gets increased twice at this point of time...to be on the safe side, set timeout to 1000ms ;) — Igl3
– Igl3, Commented Dec 2, 2013 at 8:48
@Igle Thanks for the explanation, I was wondering what was wrong with it. The timeout trick you gave me definitely also fixed the problem! — WToa
– WToa, Commented Dec 2, 2013 at 8:52

maček · Accepted Answer · 2013-12-02 08:55:07Z

5

You will want to use window.setInterval

var m = 0,
    mon = document.getElementById('mon');

var interval = window.setInterval(function() {
  m += 10;
  mon.innerHTML = "money: " + m;
}, 30000);

If for whatever reason you would like to stop adding money, you can use window.clearInterval

// stop collecting monies!
clearInterval(interval);

Here's a jsbin.com demo

edited Dec 2, 2013 at 8:55

answered Dec 2, 2013 at 8:45

maček

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1 Comment

WToa Over a year ago

Perfect! Thank you. I will accept the answer once I am able to.

AurA · Accepted Answer · 2013-12-02 08:45:11Z

0

Add a small change to it

if(s == 30 || s == 0)

This is because in the system the seconds counter gets reset to 0 after it crosses 60

answered Dec 2, 2013 at 8:45

AurA

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Comments

Claudi · Accepted Answer · 2013-12-02 08:46:24Z

0

The reason is that variable s is being rewritten in time intervals of 500ms (so the s++ trick does not work). Either increase the interval or use a global variable to store the last time.

answered Dec 2, 2013 at 8:46

Claudi

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