[javascript] less than 10 add 0 to number

How can I modify this code to add a 0 before any digits lower than 10

$('#detect').html( toGeo(apX, screenX)  + latT +', '+ toGeo(apY, screenY) + lonT  );

function toGeo(d, max) {
   var c = '';

   var r = d/max * 180;
   var deg = Math.floor(r);
   c += deg + "° ";

   r = (r - deg) * 60;
   var min = Math.floor(r);
   c += min + "' ";

   r = (r - min) * 60;
   var sec = Math.floor(r);
   c += sec + """;

   return c;
}

So the outpout would change from

4° 7' 34"W, 168° 1' 23"N

to

04° 07' 34"W, 168° 01' 23"N

Thanks for your time

Hope, this help:

Number.prototype.zeroFill= function (n) {
    var isNegative = this < 0;
    var number = isNegative ? -1 * this : this;
    for (var i = number.toString().length; i < n; i++) {
        number = '0' + number;
    }
    return (isNegative ? '-' : '') + number;
}

I was bored and playing around JSPerf trying to beat the currently selected answer prepending a zero no matter what and using slice(-2). It's a clever approach but the performance gets a lot worse as the string gets longer.

For numbers zero to ten (one and two character strings) I was able to beat by about ten percent, and the fastest approach was much better when dealing with longer strings by using charAt so it doesn't have to traverse the whole string.

This follow is not quit as simple as slice(-2) but is 86%-89% faster when used across mostly 3 digit numbers (3 character strings).

var prepended = ( 1 === string.length && string.charAt( 0 ) !== "0" ) ? '0' + string : string;

$('#detect').html( toGeo(apX, screenX)  + latT +', '+ toGeo(apY, screenY) + lonT  );

function toGeo(d, max) {
   var c = '';

   var r = d/max * 180;
   var deg = Math.floor(r);
   if(deg < 10) deg = '0' + deg;
   c += deg + "° ";

   r = (r - deg) * 60;
   var min = Math.floor(r);
   if(min < 10) min = '0' + min;
   c += min + "' ";

   r = (r - min) * 60;
   var sec = Math.floor(r);
   if(sec < 10) sec = '0' + sec;
   c += sec + """;

   return c;
}

You can always do

('0' + deg).slice(-2)

If you use it very often, you may extend the object Number

Number.prototype.pad = function(n) {
    if (n==undefined)
        n = 2;

    return (new Array(n).join('0') + this).slice(-n);
}

deg.pad(4) // "0045"

where you can set any pad size or leave the default 2.

if(myNumber.toString().length < 2)
   myNumber= "0"+myNumber;

or:

return (myNumber.toString().length < 2) ? "0"+myNumber : myNumber;

Make a function that you can reuse:

function minTwoDigits(n) {
  return (n < 10 ? '0' : '') + n;
}

Then use it in each part of the coordinates:

c += minTwoDigits(deg) + "° ";

and so on.

You can write a generic function to do this...

var numberFormat = function(number, width) {
    return new Array(+width + 1 - (number + '').length).join('0') + number;
}

jsFiddle.

That way, it's not a problem to deal with any arbitrarily width.

Here is Genaric function for add any number of leading zeros for making any size of numeric string.

function add_zero(your_number, length) {
    var num = '' + your_number;
    while (num.length < length) {
        num = '0' + num;
    }
    return num;
}

A single regular expression replace should do it:

var stringWithSmallIntegers = "4° 7' 34"W, 168° 1' 23"N";

var paddedString = stringWithSmallIntegers.replace(
    /\d+/g,
    function pad(digits) {
        return digits.length === 1 ? '0' + digits : digits;
    });

alert(paddedString);

shows the expected output.