How to convert decimal to hexadecimal in JavaScript

Question

How do you convert decimal values to their hexadecimal equivalent in JavaScript

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rgb 255  255  255     returns FFFFFF  rgb 255  255  300     returns FFFFFF  rgb 0 0 0             returns 000000  rgb 148  0  211       returns 9400D3  function rgb    values             return values reduce  acc  cur    gt                let val   cur  gt   255    ff    cur  lt   0    00    Number cur  toString 16               return acc    val length     1    0  val   val                    toUpperCase

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Here s a trimmed down ECMAScript nbsp 6 version   const convert       bin2dec   s   gt  parseInt s  2  toString 10     bin2hex   s   gt  parseInt s  2  toString 16     dec2bin   s   gt  parseInt s  10  toString 2     dec2hex   s   gt  parseInt s  10  toString 16     hex2bin   s   gt  parseInt s  16  toString 2     hex2dec   s   gt  parseInt s  16  toString 10      convert bin2dec  111        7  convert dec2hex  42         2a  convert hex2bin  f8         11111000  convert dec2bin  22         10110

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AFAIK comment 57807 is wrong and should be something like  var hex   Number d  toString 16   instead of var hex   parseInt d  16    function decimalToHex d  padding        var hex   Number d  toString 16       padding   typeof  padding       undefined     padding     null   padding   2   padding       while  hex length  lt  padding            hex    0    hex             return hex

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For completeness  if you want the two s-complement hexadecimal representation of a negative number  you can use the zero-fill-right shift  gt  gt  gt  operator  For instance      gt   -1  toString 16   -1    gt    -2  gt  gt  gt 0  toString 16   fffffffe    There is however one limitation  JavaScript bitwise operators treat their operands as a sequence of 32 bits  that is  you get the 32-bits two s complement

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If you want to convert a number to a hexadecimal representation of an RGBA color value  I ve found this to be the most useful combination of several tips from here   function toHexString n        if n  lt  0            n   0xFFFFFFFF   n   1            return  0x      00000000    n toString 16  toUpperCase    substr -8

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Here s my solution   hex   function number      return  0x    Math abs number  toString 16       The question says   How to convert decimal to hexadecimal in JavaScript   While  the question does not specify that the hexadecimal string should begin with a 0x prefix  anybody who writes code should know that 0x is added to hexadecimal codes to distinguish hexadecimal codes from programmatic identifiers and other numbers  1234 could be hexadecimal  decimal  or even octal    Therefore  to correctly answer this question  for the purpose of script-writing  you must add the 0x prefix   The Math abs N  function converts negatives to positives  and as a bonus  it doesn t look like somebody ran it through a wood-chipper   The answer I wanted  would have had a field-width specifier  so we could for example show 8 16 32 64-bit values the way you would see them listed in a hexadecimal editing application  That  is the actual  correct answer

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I m doing conversion to hex string in a pretty large loop  so I tried several techniques in order to find the fastest one  My requirements were to have a fixed-length string as a result  and encode negative values properly  -1    ff  f    Simple  toString 16  didn t work for me since I needed negative values to be properly encoded  The following code is the quickest I ve tested so far on 1-2 byte values  note that symbols defines the number of output symbols you want to get  that is for 4-byte integer it should be equal to 8    var hex     0    1    2    3    4    5    6    7    8    9    a    b    c    d    e    f    function getHexRepresentation num  symbols        var result           while  symbols--            result   hex num  amp  0xF    result          num  gt  gt   4            return result      It performs faster than  toString 16  on 1-2 byte numbers and slower on larger numbers  when symbols    6   but still should outperform methods that encode negative values properly

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This is based on Prestaul and Tod s solutions  However  this is a generalisation that accounts for varying size of a variable  e g  Parsing signed value from a microcontroller serial log     function decimalToPaddedHexString number  bitsize       let byteCount   Math ceil bitsize 8     let maxBinValue   Math pow 2  bitsize -1        In node js this function fails for bitsize above 32bits      if  bitsize  gt  32      throw  number above maximum value         Conversion to unsigned form based on       if  number  lt  0      number   maxBinValue   number   1     return  0x   number  gt  gt  gt  0  toString 16  toUpperCase   padStart byteCount 2   0        Test script   for  let n   0   n  lt  64   n             let s decimalToPaddedHexString -1  n         console log  decimalToPaddedHexString -1    n     padStart 2        s padStart 10         0b  parseInt s  toString 2   padStart 34             Test results   decimalToPaddedHexString -1  0           0x0                                  0b0 decimalToPaddedHexString -1  1          0x01                                  0b1 decimalToPaddedHexString -1  2          0x03                                 0b11 decimalToPaddedHexString -1  3          0x07                                0b111 decimalToPaddedHexString -1  4          0x0F                               0b1111 decimalToPaddedHexString -1  5          0x1F                              0b11111 decimalToPaddedHexString -1  6          0x3F                             0b111111 decimalToPaddedHexString -1  7          0x7F                            0b1111111 decimalToPaddedHexString -1  8          0xFF                           0b11111111 decimalToPaddedHexString -1  9        0x01FF                          0b111111111 decimalToPaddedHexString -1 10        0x03FF                         0b1111111111 decimalToPaddedHexString -1 11        0x07FF                        0b11111111111 decimalToPaddedHexString -1 12        0x0FFF                       0b111111111111 decimalToPaddedHexString -1 13        0x1FFF                      0b1111111111111 decimalToPaddedHexString -1 14        0x3FFF                     0b11111111111111 decimalToPaddedHexString -1 15        0x7FFF                    0b111111111111111 decimalToPaddedHexString -1 16        0xFFFF                   0b1111111111111111 decimalToPaddedHexString -1 17      0x01FFFF                  0b11111111111111111 decimalToPaddedHexString -1 18      0x03FFFF                 0b111111111111111111 decimalToPaddedHexString -1 19      0x07FFFF                0b1111111111111111111 decimalToPaddedHexString -1 20      0x0FFFFF               0b11111111111111111111 decimalToPaddedHexString -1 21      0x1FFFFF              0b111111111111111111111 decimalToPaddedHexString -1 22      0x3FFFFF             0b1111111111111111111111 decimalToPaddedHexString -1 23      0x7FFFFF            0b11111111111111111111111 decimalToPaddedHexString -1 24      0xFFFFFF           0b111111111111111111111111 decimalToPaddedHexString -1 25    0x01FFFFFF          0b1111111111111111111111111 decimalToPaddedHexString -1 26    0x03FFFFFF         0b11111111111111111111111111 decimalToPaddedHexString -1 27    0x07FFFFFF        0b111111111111111111111111111 decimalToPaddedHexString -1 28    0x0FFFFFFF       0b1111111111111111111111111111 decimalToPaddedHexString -1 29    0x1FFFFFFF      0b11111111111111111111111111111 decimalToPaddedHexString -1 30    0x3FFFFFFF     0b111111111111111111111111111111 decimalToPaddedHexString -1 31    0x7FFFFFFF    0b1111111111111111111111111111111 decimalToPaddedHexString -1 32    0xFFFFFFFF   0b11111111111111111111111111111111 Thrown   number above maximum value    Note  Not too sure why it fails above 32 bitsize

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And if the number is negative   Here is my version   function hexdec  hex string        hex string   hex string charAt 1    X   amp  amp  hex string charAt 1    x   hex string  0X  hex string   hex string       hex string  hex string charAt 2  lt 8   hex string  hex string-0x00000000   hex string hex string-0xFFFFFFFF-1       return parseInt hex string  10

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To sum it all up   function toHex i  pad       if  typeof pad       undefined     pad     null        pad   2          var strToParse   i toString 16      while  strToParse length  lt  pad        strToParse    0    strToParse         var finalVal    parseInt strToParse  16      if   finalVal  lt  0         finalVal   0xFFFFFFFF   finalVal   1         return finalVal      However  if you don t need to convert it back to an integer at the end  i e  for colors   then just making sure the values aren t negative should suffice

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You can do something like this in ECMAScript nbsp 6   const toHex   num   gt   num  toString 16  toUpperCase

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In case you re looking to convert to a  full  JavaScript or CSS representation  you can use something like     numToHex   function num        var r   0xff0000 amp num  gt  gt 16  toString 16           g   0x00ff00 amp num  gt  gt 8  toString 16           b  0x0000ff amp num  toString 16       if  r length  1    r    0  r        if  g length  1    g    0  g        if  b length  1    b    0  b        return  0x  r g b                          instead of 0x  for CSS          var dec   5974678    console log  numToHex dec               0x5b2a96

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Without the loop   function decimalToHex d      var hex   Number d  toString 16     hex    000000  substr 0  6 - hex length    hex    return hex        Or   000000  substr 0  7 - hex length    hex     Or whatever     Thanks to MSDN   Also isn t it better not to use loop tests that have to be evaluated   For example  instead of   for  var i   0  i  lt  hex length  i        have  for  var i   0  var j   hex length  i  lt  j  i

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Arbitrary precision This solution take on input decimal string  and return hex string  A decimal fractions are supported  Algorithm  split number to sign  s   integer part  i  and fractional part  f  e g for -123 75 we have s true  i 123  f 75 integer part to hex   if i  0  stop get modulo  m i 16  in arbitrary precision  convert m to hex digit and put to result string for next step calc integer part i i 16  in arbitrary precision    fractional part  count fractional digits n multiply k f 16  in arbitrary precision  split k to right part with n digits and put them to f  and left part with rest of digits and put them to d convert d to hex and add to result  finish when number of result fractional digits is enough     x000D   x000D      param decStr - string with non-negative integer     param divisor - positive integer function dec2HexArbitrary decStr  fracDigits 0              Helper  divide arbitrary precision number by js number         param decStr - string with non-negative integer         param divisor - positive integer     function arbDivision decStr  divisor                     algorithm https   www geeksforgeeks org divide-large-number-represented-string          let ans              let idx   0           let temp    decStr idx            while  temp  lt  divisor  temp   temp   10    decStr   idx             while  decStr length  gt  idx                 ans     temp   divisor  0                temp    temp   divisor    10    decStr   idx                        if  ans length    0  return  0             return ans                  Helper  calc module of arbitrary precision number         param decStr - string with non-negative integer         param mod - positive integer     function arbMod decStr  mod              algorithm https   www geeksforgeeks org how-to-compute-mod-of-a-big-number        let res   0          for  let i   0  i  lt  decStr length  i             res    res   10    decStr i     mod          return res                  Helper  multiply arbitrary precision integer by js number         param decStr - string with non-negative integer         param mult - positive integer     function arbMultiply decStr  mult          let r           let m 0        for  let i   decStr length-1  i  gt  0   i--            let n   m mult   decStr i            r   i   n 10   n    r          m  n 10 0                return r                         dec2hex algorithm starts here          let h   0123456789abcdef                                              hex  alphabet      let m  decStr match  -                   decStr match  -              separate sign integer ractional     let i  m 1  replace   0       replace       0                         integer part  without sign and leading zeros      let f   m 2    0   replace  0        replace       0                  fractional part  without last zeros      let s  decStr 0    -                                                                                  sign      let r                                                                                                                 result          if i   0   r  0                while i   0                                                           integer part       r h arbMod i 16   r         i arbDivision i 16                          if fracDigits  r                    let n   f length           for let j 0  j lt fracDigits  j                                          frac part       let k  arbMultiply f 16         f   k slice -n         let d  k slice 0 k length-n          r   d length   h  d     0                          return  s  -      r               -----------    TESTS    -----------    let tests         0  2       000  2         123  0       -123  0         00 000  2          255 75  5       -255 75  5        127 999  32        console log  Input      Standard          Abitrary    tests forEach t  gt      let nonArb     t 0   toString 16  padEnd 17         let arb   dec2HexArbitrary t 0  t 1      console log t 0  padEnd 10       nonArb  arb             Long Example  40 digits after dot  let example    123456789012345678901234567890 09876543210987654321  console log   nLong Example     console log  dec   example   console log  hex        dec2HexArbitrary example 40    x000D   x000D   x000D

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Constrained padded to a set number of characters   function decimalToHex decimal  chars        return  decimal   Math pow 16  chars   toString 16  slice -chars  toUpperCase

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If you need to handle things like bit fields or 32-bit colors  then you need to deal with signed numbers  The JavaScript function toString 16  will return a negative hexadecimal number which is usually not what you want  This function does some crazy addition to make it a positive number    x000D   x000D  function decimalToHexString number  x000D    x000D    if  number  lt  0  x000D      x000D      number   0xFFFFFFFF   number   1  x000D      x000D   x000D    return number toString 16  toUpperCase    x000D    x000D   x000D  console log decimalToHexString 27    x000D  console log decimalToHexString 48 6    x000D   x000D   x000D

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How to convert decimal to hexadecimal in JavaScript  I wasn t able to find a brutally clean simple decimal to hexadecimal conversion that didn t involve a mess of functions and arrays     so I had to make this for myself   function DecToHex decimal       Data  decimal       length   -1        Base string length     string             Source  string       characters      0    1    2    3    4    5    6    7    8    9    A    B    C    D    E    F        character array      do      Grab each nibble in reverse order because JavaScript has no unsigned left shift          string    characters decimal  amp  0xF        Mask byte  get that character           length                                  Increment to length of string        while  decimal  gt  gt  gt   4      For next character shift right 4 bits  or break on 0      decimal     x      Convert that 0 into a hex prefix string - gt   0x       do         decimal    string length       while  length--      Flip string forwards  with the prefixed  0x       return  decimal      return  hexadecimal         Original      D   3678        Data  decimal  C   0xF        Check A   D            Accumulate B   -1            Base string length S                 Source  string  H    0x         Destination  string   do         B      A amp    C       switch A            case 0xA  A  A          break           case 0xB  A  B          break           case 0xC  A  C          break           case 0xD  A  D          break           case 0xE  A  E          break           case 0xF  A  F          break           A    A             S    A       D  gt  gt  gt   0x04      A   D    while D   do     H    S B   while  B--   S   B   A   C   D     Zero out variables alert H         H  holds hexadecimal equivalent

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For anyone interested  here s a JSFiddle comparing most of the answers given to this question   And here s the method I ended up going with   function decToHex dec      return  dec   Math pow 16  6   toString 16  substr -6        Also  bear in mind that if you re looking to convert from decimal to hex for use in CSS as a color data type  you might instead prefer to extract the RGB values from the decimal and use rgb     For example  JSFiddle    let c   4210330    your color in decimal format let rgb     c  amp  0xff0000   gt  gt  16    c  amp  0x00ff00   gt  gt  8    c  amp  0x0000ff       Vanilla JS  document  getElementById  some-element   style color    rgb     rgb          jQuery      some-element   css  color    rgb     rgb          This sets  some-element s CSS color property to rgb 64  62  154

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If you are looking for converting Large integers i e  Numbers greater than Number MAX SAFE INTEGER -- 9007199254740991  then you can use the following code   x000D   x000D  const hugeNumber    9007199254740991873839     Make sure its in String x000D  const hexOfHugeNumber   BigInt hugeNumber  toString 16   x000D  console log hexOfHugeNumber  x000D   x000D   x000D

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Convert a number to a hexadecimal string with   hexString   yourNumber toString 16     And reverse the process with   yourNumber   parseInt hexString  16

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The accepted answer did not take into account single digit returned hexadecimal codes  This is easily adjusted by   function numHex s        var a   s toString 16       if   a length   2   gt  0            a    0    a            return a      and  function strHex s        var a           for  var i 0  i lt s length  i              a   a   numHex s charCodeAt i               return a      I believe the above answers have been posted numerous times by others in one form or another  I wrap these in a toHex   function like so   function toHex s        var re   new RegExp    s     -     d     d         d    s           if  re test s             return       strHex  s toString               else           return  A    strHex s             Note that the numeric regular expression came from 10  Useful JavaScript Regular Expression Functions to improve your web applications efficiency   Update  After testing this thing several times I found an error  double quotes in the RegExp   so I fixed that   HOWEVER  After quite a bit of testing and having read the post by almaz - I realized I could not get negative numbers to work    Further - I did some reading up on this and since all JavaScript numbers are stored as 64 bit words no matter what - I tried modifying the numHex code to get the 64 bit word  But it turns out you can not do that  If you put  3 14159265  AS A NUMBER into a variable - all you will be able to get is the  3   because the fractional portion is only accessible by multiplying the number by ten IE 10 0  repeatedly  Or to put that another way - the hexadecimal value of 0xF causes the floating point value to be translated into an integer before it is ANDed which removes everything behind the period   Rather than taking the value as a whole  i e   3 14159265  and ANDing the floating point value against the 0xF value   So the best thing to do  in this case  is to convert the 3 14159265 into a string and then just convert the string  Because of the above  it also makes it easy to convert negative numbers because the minus sign just becomes 0x26 on the front of the value   So what I did was on determining that the variable contains a number - just convert it to a string and convert the string  This means to everyone that on the server side you will need to unhex the incoming string and then to determine the incoming information is numeric  You can do that easily by just adding a     to the front of numbers and  A  to the front of a character string coming back  See the toHex   function   Have fun   After another year and a lot of thinking  I decided that the  toHex  function  and I also have a  fromHex  function  really needed to be revamped  The whole question was  How can I do this more efficiently   I decided that a to from hexadecimal function should not care if something is a fractional part but at the same time it should ensure that fractional parts are included in the string   So then the question became   How do you know you are working with a hexadecimal string    The answer is simple  Use the standard pre-string information that is already recognized around the world   In other words - use  0x   So now my toHex function looks to see if that is already there and if it is - it just returns the string that was sent to it  Otherwise  it converts the string  number  whatever  Here is the revised toHex function                                                                                     toHex     Convert an ASCII string to hexadecimal                                                                                toHex s        if  s substr 0 2  toLowerCase       0x             return s             var l    0123456789ABCDEF       var o            if  typeof s     string             s   s toString              for  var i 0  i lt s length  i              var c   s charCodeAt i            o   o   l substr  c gt  gt 4  1    l substr  c  amp  0x0f  1              return  0x    o      This is a very fast function that takes into account single digits  floating point numbers  and even checks to see if the person is sending a hex value over to be hexed again  It only uses four function calls and only two of those are in the loop  To un-hex the values you use                                                                                     fromHex     Convert a hex string to ASCII text                                                                                fromHex s        var start   0      var o            if  s substr 0 2  toLowerCase       0x             start   2             if  typeof s     string             s   s toString              for  var i start  i lt s length  i  2            var c   s substr i  2            o   o   String fromCharCode parseInt c  16               return o      Like the toHex   function  the fromHex   function first looks for the  0x  and then it translates the incoming information into a string if it isn t already a string   I don t know how it wouldn t be a string - but just in case - I check  The function then goes through  grabbing two characters and translating those in to ASCII characters  If you want it to translate Unicode  you will need to change the loop to going by four 4  characters at a time  But then you also need to ensure that the string is NOT divisible by four  If it is - then it is a standard hexadecimal string   Remember the string has  0x  on the front of it    A simple test script to show that -3 14159265  when converted to a string  is still -3 14159265    lt  php      echo  lt  lt  lt EOD  lt html gt       lt head gt  lt title gt Test lt  title gt           lt script gt              var a   -3 14159265              alert   A       a                var b   a toString                alert   B       b             lt  script gt       lt  head gt       lt body gt       lt  body gt   lt  html gt  EOD     gt    Because of how JavaScript works in respect to the toString   function  all of those problems can be eliminated which before were causing problems  Now all strings and numbers can be converted easily  Further  such things as objects will cause an error to be generated by JavaScript itself  I believe this is about as good as it gets  The only improvement left is for W3C to just include a toHex   and fromHex   function in JavaScript

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With padding   function dec2hex i       return  i 0x10000  toString 16  substr -4  toUpperCase

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var number   3200  var hexString   number toString 16     The 16 is the radix and there are 16 values in a hexadecimal number  -

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function dec2hex i      var result    0000     if       i  gt   0     amp  amp  i  lt   15       result    000    i toString 16       else if  i  gt   16    amp  amp  i  lt   255      result    00     i toString 16       else if  i  gt   256   amp  amp  i  lt   4095     result    0      i toString 16       else if  i  gt   4096  amp  amp  i  lt   65535    result           i toString 16       return result

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function toHex d        return    0   Number d  toString 16    slice -2  toUpperCase

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I haven t found a clear answer  without checks if it is negative or positive  that uses two s complement  negative numbers included   For that  I show my solution to one byte     0xFF   number  1   amp  0x0FF  toString 16     You can use this instruction to any number bytes  only you add FF in respective places  For example  to two bytes     0xFFFF   number  1   amp  0x0FFFF  toString 16     If you want cast an array integer to string hexadecimal   s       for var i   0  i  lt  arrayNumber length    i        s      0xFF   arrayNumber i   1   amp  0x0FF  toString 16

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Combining some of these good ideas for an RGB-value-to-hexadecimal function  add the   elsewhere for HTML CSS    function rgb2hex r g b        if  g     undefined          return Number 0x1000000   r 0x10000   g 0x100   b  toString 16  substring 1       else         return Number 0x1000000   r 0  0x10000   r 1  0x100   r 2   toString 16  substring 1

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As the accepted answer states  the easiest way to convert from decimal to hexadecimal is var hex   dec toString 16   However  you may prefer to add a string conversion  as it ensures that string representations like  12  toString 16  work correctly      Avoids a hard-to-track-down bug by returning  c  instead of  12     12   toString 16     To reverse the process you may also use the solution below  as it is even shorter   var dec      0x    hex     It seems to be slower in Google Chrome and Firefox  but is significantly faster in Opera  See http   jsperf com hex-to-dec

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The code below will convert the decimal value d to hexadecimal  It also allows you to add padding to the hexadecimal result  So 0 will become 00 by default   function decimalToHex d  padding        var hex   Number d  toString 16       padding   typeof  padding       undefined     padding     null   padding   2   padding       while  hex length  lt  padding            hex    0    hex             return hex

[javascript] How to convert decimal to hexadecimal in JavaScript

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