javascript adding minutes in a loop

Question

Can't figure this out, from 9:00 to 10:00 everything's correct, but then it all goes haywire. after 10:00 it jumps to 11:15 and then to 12:30

I am simply adding minutes to a date/time to increment an array in 15 minute intervals, is it that I can only add a maximum of 60 minutes ??

function pad(val,max) { 
        var str = val.toString(); 
        return str.length < max ? pad("0" + str, max) : str;
}

function cboHrs(){
    var now = new Date(); 
    now.setHours(9);
    var hrs = [];
    for (var i=1;i<36;i++){
        var hr = {}; 
        now.setMinutes(i*15);
        hr.txt = pad(now.getHours(),2) +':'+pad(now.getMinutes(),2);
        hr.val = hr.txt; 
        hrs.push(hr);
        }
    return hrs;
}
console.log(cboHrs());

Can you post the pad function?

bcoughlan
– bcoughlan

2013-03-20 12:11:14 +00:00
Commented Mar 20, 2013 at 12:11 — bcoughlan
– bcoughlan, Commented Mar 20, 2013 at 12:11

jonhopkins · Accepted Answer · 2013-03-20 12:19:22Z

3

Anthony got to the actual problem before me...

After the 5th iteration, you are setting the minutes to become 75 (ie, 5 * 15 = 75) which is an 1 hour and 15 minutes which is why the next value after 10:00 becomes 11:15 - Anthony Forloney

This code should work to set the time correctly.

function cboHrs(){
    var now = new Date(); 
    var hrs = [];
    for (var i=1;i<36;i++){
        var hr = {};
        // add another hour every 4th iteration
        now.setHours(9 + parseInt(i / 4));
        // add 15 minutes every iteration, starting back at 0 on the 4th
        now.setMinutes((i % 4) * 15);
        hr.txt = pad(now.getHours(),2) +':'+pad(now.getMinutes(),2);
        hr.val = hr.txt; 
        hrs.push(hr);
        }
    return hrs;
}

answered Mar 20, 2013 at 12:19

jonhopkins

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1 Comment

jonhopkins Over a year ago

No problem. I actually would have expected the same behavior you were expecting and as a result would have run into the same problem, so I'm glad this question got me thinking about it, potentially saving me, and hopefully others, some time.

Anthony Forloney · Accepted Answer · 2013-03-20 12:18:19Z

2

The problem lies within the now.setMinutes(i*15); line of code. After the 5th iteration, you are setting the minutes to become 75 (ie, 5 * 15 = 75) which is an 1 hour and 15 minutes which is why the next value after 10:00 becomes 11:15

answered Mar 20, 2013 at 12:18

Anthony Forloney

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