How to format numbers by prepending 0 to single-digit numbers

Question

I want to format a number to have two digits  The problem is caused when 0   9 is passed  so I need it to be formatted to 00   09   Is there a number formatter in JavaScript

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function colorOf r g b     var f   function  x        return  x lt 16    0          x toString 16           return        f r    f g    f b

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Improved version of previous answer   x000D   x000D  function atLeast2Digit n   x000D      n   parseInt n     ex  if already passed  05  it will be converted to number 5 x000D      var ret   n  gt  9        n   0    n  x000D      return ret  x000D    x000D   x000D  alert atLeast2Digit 5    x000D   x000D   x000D

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For anyone who wants to have time differences and have results that can take negative numbers here is a good one  pad 3     03   pad -2     -02   pad -234     -234   pad   function n     if n  gt   0       return n  gt  9        n    0    n     else      return n  lt  -9        n    -0    Math abs n

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Here s a simple recursive solution that works for any number of digits   function numToNDigitStr num  n        if num  gt    Math pow 10  n - 1     return num        return  0    numToNDigitStr num  n-1

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Edit  2021   It s no longer necessary to format numbers by hand like this anymore   This answer was written way-back-when in the distant year of 2011 when IE was important and babel and bundlers were just a wonderful  hopeful dream  I think it would be a mistake to delete this answer  however in case you find yourself here  I would like to kindly direct your attention to the second highest voted answer to this question as of this edit  It will introduce you to the use of  toLocaleString   with the options parameter of  minimumIntegerDigits  2    Exciting stuff   Below I ve recreated all three examples from my original answer using this method for your convenience   x000D   x000D   7  7 5  -7 2345  forEach myNumber   gt      let formattedNumber   myNumber toLocaleString  en-US         minimumIntegerDigits  2      useGrouping  false        console log       Input         myNumber     n         Output        formattedNumber        x000D   x000D   x000D    Original Answer  The best method I ve found is something like the following   Note that this simple version only works for positive integers   x000D   x000D  var myNumber   7  var formattedNumber     0    myNumber  slice -2   console log formattedNumber   x000D   x000D   x000D   For decimals  you could use this code  it s a bit sloppy though    x000D   x000D  var myNumber   7 5  var dec   myNumber - Math floor myNumber   myNumber   myNumber - dec  var formattedNumber     0    myNumber  slice -2    dec toString   substr 1   console log formattedNumber   x000D   x000D   x000D   Lastly  if you re having to deal with the possibility of negative numbers  it s best to store the sign  apply the formatting to the absolute value of the number  and reapply the sign after the fact   Note that this method doesn t restrict the number to 2 total digits   Instead it only restricts the number to the left of the decimal  the integer part    The line that determines the sign was found here    x000D   x000D  var myNumber   -7 2345  var sign   myNumber myNumber lt 0 -1 1 0  myNumber   myNumber   sign          poor man s absolute value var dec   myNumber match     d      var int   myNumber match              var formattedNumber    sign  lt  0    -            0    int  slice -2     dec     null   dec        console log formattedNumber   x000D   x000D   x000D

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There is not a built-in number formatter for JavaScript  but there are some libraries that accomplish this    underscore string provides an sprintf function  along with many other useful formatters  javascript-sprintf  which underscore string borrows from

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with this function you can print with any n digits you want  function frmtDigit num  n        isMinus   num  lt  0      if  isMinus          num    -1      digit           if  typeof n     undefined           n   2   two digits     for  i   1  i  lt  n  i              if  num  lt   1   Array i   1  join  0                 digit     0             digit    isMinus    -          digit   num      return digit

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number   replace     d      0 1     Regex is the best

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If the number is higher than 9  convert the number to a string  consistency   Otherwise  add a zero   function n n       return n  gt  9        n   0    n     n  9     Returns  09  n 10     Returns  10  n 999    Returns  999

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Here s my version  Can easily be adapted to other scenarios   function setNumericFormat value        var length   value toString   length      if  length  lt  4            var prefix               for  var i   1  i  lt   4 - length  i                  prefix     0                     return prefix   value toString              return  value toString

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or   function zpad n l      return rep l-n toString   length   0     n toString        with  function rep len  chr        return new Array len 1  join chr

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Updated for ES6 Arrow Functions  Supported in almost all modern browsers  see CanIUse   const formatNumber   n   gt    0    n  slice -2

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You can do   function pad2 number       return  number  lt  10    0          number     Example   document write pad2 0      lt br   gt     document write pad2 1      lt br   gt     document write pad2 2      lt br   gt     document write pad2 10      lt br   gt     document write pad2 15      lt br   gt         Result   00 01 02 10 15

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It seems you might have a string  instead of a number  use this   var num   document getElementById  input   value      replacement   num replace     d      0 1    document getElementById  input   value   replacement    Here s an example  http   jsfiddle net xtgFp

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My version     Math trunc num   10    Math trunc num   10       x000D   x000D  const func    num    gt     Math trunc num   10    Math trunc num   10      const nums    1  3  5  6  8  9  10  20  56  80   nums forEach num   gt  console log func num     x000D   x000D   x000D

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Use the toLocaleString   method in any number  So for the number 6  as seen below  you can get the desired results    6  toLocaleString  en-US    minimumIntegerDigits  2  useGrouping false     Will generate the string  06

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You can use the padStart method  more info  https   developer mozilla org es docs Web JavaScript Referencia Objetos globales String  check this example   x000D   x000D  function n num      return    num   padStart 2   0       console log n  9       print  09  console log n 10       print  10  console log n 999      print  999  x000D   x000D   x000D

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If you don t have lodash in your project it will be an overkill to add the whole library just to use one function  This is the most sophisticated solution of your problem I ve ever seen     padStart num  2   0

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Lifehack s answer was very useful to me  where I think we can do it in one line for positive numbers   String input  padStart 2   0

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I built a pretty simple format function that I call whenever I need a simple date formatted  It deals with formatting single digits to double digits when they re less than 10  It kicks out a date formatted as Sat Sep 29 2018 - 00 05 44  This function is used as part of a utils variable so it s called as    let timestamp   utils  dateFormatter  your date string     var utils        dateFormatter  function dateString        let d   new Date dateString       let hours   d getHours        let minutes   d getMinutes        let seconds   d getSeconds        d   d toDateString        if  hours  lt  10          hours    0    hours            if  minutes  lt  10          minutes    0    minutes            if  seconds  lt  10          seconds    0    seconds            let formattedDate   d     -     hours         minutes         seconds      return formattedDate

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AS datatype in Javascript are determined dynamically it treats 04 as 4  Use conditional statement if value is lesser then 10 then add 0 before it by make it string  E g   var x 4    x   x lt 10  0  x x  console log x      04

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Here is a very simple solution that worked well for me   First declare a variable to hold your number   var number    Now convert the number to a string and hold it in another variable   var numberStr   number toString      Now you can test the length of this string   if it is less than desired you can append a  zero  at the beginning   if numberStr length  lt  2         number    0    number      Now use the number as desired  console log number

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lt html gt       lt head gt           lt script src  http   code jquery com jquery-1 11 0 min js  gt  lt  script gt           lt script type  text javascript  gt                document  ready function                        test   keypress allowOnlyTwoPositiveDigts                                function allowOnlyTwoPositiveDigts e                    var test       -   0-9  1 2                     return test test this value String fromCharCode e which                           lt  script gt       lt  head gt       lt body gt           lt input id  test  type  text    gt       lt  body gt   lt  html gt

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Here s the easiest solution I found -  let num   9     any number between 0  amp  99 let result      0    num   substr  -2

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0     date getMonth     1   slice -2     0     date getDay     slice -2

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Here s a simple number padding function that I use usually  It allows for any amount of padding   function leftPad number  targetLength        var output   number           while  output length  lt  targetLength            output    0    output            return output      Examples   leftPad 1  2     01 leftPad 10  2     10 leftPad 100  2     100 leftPad 1  3     001 leftPad 1  8     00000001

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This is a very nice and short solution  smartTime time      return time  lt  10    quot 0 quot    time toString   trim     time

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my example would be    lt div id  showTime  gt  lt  div gt       function x         var showTime   document getElementById  showTime        var myTime   new Date        var hour   myTime getHours        var minu   myTime getMinutes        var secs   myTime getSeconds        if  hour  lt  10            hour    0    hour            if  minu  lt  10            minu    0    minu            if  secs  lt  10            secs    0    secs             showTime innerHTML   hour         minu         secs     setInterval  x     1000

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This is simple and works pretty well   function twoDigit number      var twodigit   number  gt   10   number    0  number toString      return twodigit

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I know this is an ancient post  but I wanted to provide a more flexible and OO solution option   I ve extrapolated the accepted answer a bit and extended javascript s Number object to allow for adjustable zero padding    x000D   x000D  Number prototype zeroPad   function digits    x000D    var loop   digits  x000D    var zeros       x000D    while  loop    x000D      zeros     0   x000D      loop--  x000D      x000D    return  this toString   length  gt  digits    x000D      this toString      zeros   this  slice -digits   x000D    x000D  var v   5  x000D  console log v zeroPad 2       returns  05  x000D  console log v zeroPad 4       returns  0005  x000D   x000D   x000D    Edit  Add code to prevent cutting off numbers longer than your requested digits   NOTE  This is obsolete in all but IE  Use padStart   instead

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In all modern browsers you can use  numberStr padStart 2   0      https   developer mozilla org en-US docs Web JavaScript Reference Global Objects String padStart   x000D   x000D  function zeroPad numberStr    x000D    return numberStr padStart 2   0    x000D    x000D   x000D  var numbers    0  1  2  3  4  5  6  7  8  9  10   x000D   x000D  numbers forEach  x000D    function num    x000D      var numString   num toString    x000D       x000D      var paddedNum   zeroPad numString   x000D   x000D      console log paddedNum   x000D      x000D     x000D   x000D   x000D

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This is an old question  but wanted to add to it  In modern browsers you may use repeat which makes formatting simple for positive numbers     0  repeat digits - 1    num  substr -digits    If you want support for IE and know the maximum number of digits  for instance  10 digits      000000000    num  substr -digits    For negative integers    num  lt  0    -            000000000    Math abs num   substr -digits    With an explicit   for positive numbers     -            Math sign num    1      000000000    Math abs num   substr -digits

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My Example like this           var n  9           var checkval   00  n  slice -2            console log checkval    and the output is 09

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Quick and dirty one liner      function zpad n  len      return 0  toFixed len  slice 2 -n toString   length  n toString

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If you want to limit your digits at the same time   function pad2 number      number    number  lt  10    0          number    number   number substring 0 2     return number      This would also chop of any value that exceeds two digits  I have been extending this upon fanaur s solution

[javascript] How to format numbers by prepending 0 to single-digit numbers?

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