Question

I am new to JavaScript (but not programming) and am having a difficult time figuring out where I made a mistake in this function, found here: http://mikeryan.webatu.com/function.html [dead link][Guessing of the original code at the bottom]

The function should take a DDMMYY timestamp and convert it into a human-readable string. For instance, 210710 would be turned into July 21st, 2010.

UPDATE: Code that is probably similar OP’s dead link:

function timestamp(d){
    var year = (d-(Math.round(d / 100)*100);

    var day = Math.floor(d/10000);
    var dayfix = (day - (Math.floor(day/10)*10));

    // var month = ((d-year)-(day*100000)/100);

    var a = (d - year);
    var b = ((day * 100000) / 10);

    var month = (a - b) / 100;

    var months = new Array();
    months[1]  = "January";
    months[2]  = "February";
    months[3]  = "March";
    months[4]  = "April";
    months[5]  = "May";
    months[6]  = "June";
    months[7]  = "July";
    months[8]  = "August";
    months[9]  = "September";
    months[10]  = "October";
    months[11] = "November";
    months[12] = "December";

    var daysuffix = new Array();
    daysuffix[0] = "th";
    daysuffix[1] = "st";
    daysuffix[2] = "nd";
    daysuffix[3] = "rd";
    daysuffix[4] = "th";
    daysuffix[5] = "th";
    daysuffix[6] = "th";
    daysuffix[7] = "th";
    daysuffix[8] = "th";
    daysuffix[9] = "th";

    if(year>20){
       year = '19' + year;
    }
    else{
       year = '20' + year;
    }
    return (months[month] + ' ' + day + daysuffix[dayfix] + ', ' + year);
 }

Answer 1

One problem: you’re missing a parenthesis. Change:

var year = (d-(Math.round(d / 100)*100);

to

var year = (d-(Math.round(d / 100)*100));

That being said, this is a more straightforward calculation method:

var year = d % 100;
var month = Math.floor(d / 100) % 100;
var day = Math.floor(d / 10000) % 100;

Next, your array initialization is unnecessarily verbose. Instead of:

var arr = new Array();
arr[0] = "foo";
arr[1] = "bar";

just do:

var arr = ["foo", "bar"];

Your day suffix is incorrect. It puts “nd” after 12 and “12nd April” clearly isn’t correct. I would just use logic for doing this rather than a lookup array where most elements are “th”.

So:

function timestamp(d){
  var year = d % 100;
  var month = Math.floor(d / 100) % 100;
  var day = Math.floor(d / 10000) % 100;
  var months = ["January", "February", "March", "April", "May", "June",
    "July", "August", "September", "October", "November", "December"];
  if (year>20) {
    year = '19' + year;
  } else {
    year = '20' + year;
  }
  if (day == 1 || day == 21 || day == 31) {
    var suffix = "st";
  } else if (day == 2 || day == 22) {
    var suffix = "nd";
  } else {
    var suffix = "th";
  }
  return (months[month-1] + ' ' + day + suffix + ', ' + year);
}

Lastly there is little value in your “timestamp” being an integer in its present form. A more typical format for tis kind of thing is YYYYMMDD for two reasons:

1. Numerical ordering matches date ordering; and

2. It’s unambiguous. North Americans put month before day (ie MMDDYY). Everyone else in the world puts day first (ie DDMMYY). No one does YYDDMM.