Question

I get back a json object from Facebook which contains some friends information.

Some users have included their birthday some have not, while others have included only the the month and day.

I want to sort the array putting users with a birthday that is closes to the current date first.

How can I do this?

The json object looks like this:

json = { "data" : [{name : "Joe Sam", id : "5555555", birthday: "02/02/1989" }, {name : "Joe Sam", id : 5555555, birthday:  }, {name : "Joe Sam", id : 5555555, birthday: "01/01" }

Answer 1

Your JSON is invalid – if that is the actual JSON string keynames need to be quoted. You have left off the closing ] and }, and the middle record’s birthday has to have some kind of value, e.g., empty string or null – or just don’t provide that key at all. I’ll assume you can fix that and will have already parsed the JSON into a variable called json.

Also you don’t say if the dates are in DD/MM(/YYYY) format or MM/DD(/YYYY) format so I’ll code for DD/MM but you can comment that out to use MM/DD instead.

“Closest to the current date” is ambiguous: is yesterday closer than next week? I shall assume that yesterday is as far from the current date as you can get.

So here’s your object tidied up along with a sort routine. I haven’t tested it, but even assuming it is broken it should give you the general idea:

var json = { "data" : [
                {name : "Joe Sam", id : "5555555", birthday: "02/02/1989" },
                {name : "Joe Sam", id : 5555555, birthday: null },
                {name : "Joe Sam", id : 5555555, birthday: "01/01" }
             ]
           };

// First sort into ascending birthday order, with people who didn't provide
// a birthday at the beginning of the list

function dayMonthComparer(a,b)
  // note double-equals null also allows for undefined "birthday" property 
  if (aBD == null)
    return bBD == null ? 0 : -1;

  if (bBD == null)
    return 1;

  // next two lines allow for DD/MM format; comment them out for MM/DD format
  aBD = aBD.substr(3,2) + aBD.substr(0,2);
  bBD = bBD.substr(3,2) + bBD.substr(0,2);

  // note: simple string compare works once in MM/DD format
  return aBD === bBD ? 0 : (aBD > bBD ? 1 : -1);
}

json["data"].sort(function(a,b) {
  return dayMonthComparer(a["birthday"],b["birthday"]);
});

// Next, find the first item in the array after the current date and
// move everything before that item to the end of the array.
var today = new Date(),
    d = today.getDate(),
    m = today.getMonth() + 1,
    current,
    firstNonBlank = null,
    firstFromCurrent = 0;

if (d < 10) d = "0" + d;
if (m < 10) d = "0" + d;

current = d + "/" m;
// or use current = m + "/" + d if using American format

// get index of first item with birthday on or after current date
while(firstFromCurrent < json["data"].length &&
      dayMonthComparer(current,json["data"][firstFromCurrent]["birthday"]) > 1) {
  if (firstNonBlank===null &&
      json["data"][firstFromCurrent]["birthday"] != null)
     firstNonBlank = firstFromCurrent;
  firstFromCurrent++;
}

if (firstFromCurrent < json["data"].length) {
  json["data"] = json["data"].slice(firstFromCurrent)
                 .concat(json["data"].slice(firstNonBlank,firstFromCurrent),
                         json["data"].slice(0,firstNonBlank) );
}

// array is now sorted by birthday starting from current date, where
// those who didn't provide a birthday are at the end

For details about how .sort() works refer to the MDN doco.