JavaScript两次添加变量

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.

Answer 1

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

Answer 2

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

Answer 3

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.