Generate a Hash from string in Javascript

Question

I need to convert strings to some form of hash   Is this possible in JavaScript   I m not utilizing a server-side language so I can t do it that way

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EDIT  based on my jsperf tests  the accepted answer is actually faster  http   jsperf com hashcodelordvlad  ORIGINAL  if anyone is interested  here is an improved   faster   version  which will fail on older browsers who lack the reduce array function   hashCode   function s     return s split     reduce function a b  a   a lt  lt 5 -a  b charCodeAt 0  return a amp a  0                     one-liner arrow function version    hashCode   s   gt  s split     reduce  a b   gt  a   a lt  lt 5 -a  b charCodeAt 0  return a amp a  0

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About half of the answers here are the same String hashCode hash function taken from Java  It dates back to 1981 from Gosling Emacs  is extremely weak  and makes zero sense performance-wise in modern JavaScript  In fact  implementations could be significantly faster by using ES6 Math imul  but no one took notice  We can do much better than this  at essentially identical performance  Here s something I did   cyrb53  a simple but high quality 53-bit hash  It s quite fast  provides very good hash distribution  and has significantly lower collision rates compared to any 32-bit hash  const cyrb53   function str  seed   0        let h1   0xdeadbeef   seed  h2   0x41c6ce57   seed      for  let i   0  ch  i  lt  str length  i              ch   str charCodeAt i           h1   Math imul h1   ch  2654435761           h2   Math imul h2   ch  1597334677             h1   Math imul h1    h1 gt  gt  gt 16   2246822507    Math imul h2    h2 gt  gt  gt 13   3266489909       h2   Math imul h2    h2 gt  gt  gt 16   2246822507    Math imul h1    h1 gt  gt  gt 13   3266489909       return 4294967296    2097151  amp  h2     h1 gt  gt  gt 0       It is similar to the well-known MurmurHash xxHash algorithms  it uses a combination of multiplication and Xorshift to generate the hash  but not as thorough  As a result it s faster than either in JavaScript and significantly simpler to implement  Furthermore  keep in mind this is not a secure algorithm  if privacy security is a concern  this is not for you  Like any proper hash  it has an avalanche effect  which basically means small changes in the input have big changes in the output making the resulting hash appear more  random    quot 501c2ba782c97901 quot    cyrb53  quot a quot    quot 459eda5bc254d2bf quot    cyrb53  quot b quot    quot fbce64cc3b748385 quot    cyrb53  quot revenge quot    quot fb1d85148d13f93a quot    cyrb53  quot revenue quot    You can also supply a seed for alternate streams of the same input   quot 76fee5e6598ccd5c quot    cyrb53  quot revenue quot   1   quot 1f672e2831253862 quot    cyrb53  quot revenue quot   2   quot 2b10de31708e6ab7 quot    cyrb53  quot revenue quot   3   Technically  it is a 64-bit hash  that is  two uncorrelated 32-bit hashes computed in parallel  but JavaScript is limited to 53-bit integers  If convenient  the full 64-bit output can be used by altering the return statement with a hex string or array  return  h2 gt  gt  gt 0  h1 gt  gt  gt 0      or return  h2 gt  gt  gt 0  toString 16  padStart 8 0   h1 gt  gt  gt 0  toString 16  padStart 8 0    Be aware that constructing hex strings drastically slows down batch processing  The array is more efficient  but obviously requires two checks instead of one   Just for fun  here s the smallest hash I could come up with that s still decent  It s a 32-bit hash in 89 chars with better quality randomness than even FNV or DJB2  TSH s  gt  for var i 0 h 9 i lt s length  h Math imul h s charCodeAt i    9  9  return h h gt  gt  gt 9

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Adding this because nobody did yet  and this seems to be asked for and implemented a lot with hashes  but it s always done very poorly     This takes a string input  and a maximum number you want the hash to equal  and produces a unique number based on the string input   You can use this to produce a unique index into an array of images  If you want to return a specific avatar for a user  chosen at random  but also chosen based on their name  so it will always be assigned to someone with that name    You can also use this  of course  to return an index into an array of colors  like for generating unique avatar background colors based on someone s name   function hashInt  str  max   1000        var hash   0      for  var i   0  i  lt  str length  i            hash     hash  lt  lt  5  - hash    str charCodeAt i         hash   hash  amp  hash            return Math round max   Math abs hash    2147483648

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I m kinda late to the party  but you can use this module  crypto    const crypto   require  crypto     const SALT     ome alt    function generateHash pass      return crypto createHmac  sha256   SALT       update pass       digest  hex        The result of this function is always is 64 characters string  something like this   aa54e7563b1964037849528e7ba068eb7767b1fab74a8d80fe300828b996714a

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My quick  very long  one liner based on FNV s Multiply Xor method   my string split     map v  gt v charCodeAt 0   reduce  a v   gt a   a lt  lt 7   a lt  lt 3   v  toString 16

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Here is a compact ES6 friendly readable snippet const stringHashCode   str   gt      let hash   0   for  let i   0  i  lt  str length    i      hash    Math imul 31  hash    str charCodeAt i     0    return hash

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Based on accepted answer in ES6  Smaller  maintainable and works in modern browsers    x000D   x000D  function hashCode str    x000D    return str split     reduce  prevHash  currVal    gt  x000D         prevHash  lt  lt  5  - prevHash    currVal charCodeAt 0   0  0   x000D    x000D   x000D     Test x000D  console log  hashCode   Hello         hashCode  Hello      x000D   x000D   x000D    EDIT  2019-11-04    one-liner arrow function version     x000D   x000D  const hashCode   s   gt  s split     reduce  a b    gt     a  lt  lt  5  - a    b charCodeAt 0   0  0  x000D   x000D     test x000D  console log hashCode  Hello     x000D   x000D   x000D

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I do not see any reason to use this overcomplicated crypto code instead of ready-to-use solutions  like object-hash library  or etc  relying on vendor is more productive  saves time and reduces maintenance cost    Just use https   github com puleos object-hash  var hash   require  object-hash     hash  foo   bar         gt   67b69634f9880a282c14a0f0cb7ba20cf5d677e9  hash  1  2  2 718  3 14159        gt   136b9b88375971dff9f1af09d7356e3e04281951

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I have combined the two solutions  users esmiralha and lordvlad  to get a function that should be faster for browsers that support the js function reduce   and still compatible with old browsers   String prototype hashCode   function          if  Array prototype reduce            return this split     reduce function a b  a   a lt  lt 5 -a  b charCodeAt 0  return a amp a  0            else            var hash   0  i  chr  len          if  this length    0  return hash          for  i   0  len   this length  i  lt  len  i              chr     this charCodeAt i           hash      hash  lt  lt  5  - hash    chr          hash    0     Convert to 32bit integer                   return hash             Example    my string    xyz   my string hashCode

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I went for a simple concatenation of char codes converted to hex strings  This serves a relatively narrow purpose  namely just needing a hash representation of a SHORT string  e g  titles  tags  to be exchanged with a server side that for not relevant reasons can t easily implement the accepted hashCode Java port  Obviously no security application here   String prototype hash   function       var self   this  range   Array this length     for var i   0  i  lt  this length  i          range i    i        return Array prototype map call range  function i        return self charCodeAt i  toString 16        join          This can be made more terse and browser-tolerant with Underscore  Example    Lorem Ipsum  hash    4c6f72656d20497073756d    I suppose if you wanted to hash larger strings in similar fashion you could just reduce the char codes and hexify the resulting sum rather than concatenate the individual characters together   String prototype hashLarge   function       var self   this  range   Array this length     for var i   0  i  lt  this length  i          range i    i        return Array prototype reduce call range  function sum  i        return sum   self charCodeAt i        0  toString 16       One time  I hired a monkey to take notes for me in class  I would just sit back with my mind completely blank while the monkey scribbled on little pieces of paper  At the end of the week  the teacher said   Class  I want you to write a paper using your notes   So I wrote a paper that said   Hello  My name is Bingo  I like to climb on things  Can I have a banana  Eek  eek   I got an F  When I told my mom about it  she said   I told you  never trust a monkey    hashLarge    9ce7    Naturally more risk of collision with this method  though you could fiddle with the arithmetic in the reduce however you wanted to diversify and lengthen the hash

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If you want to avoid collisions you may want to use a secure hash like SHA-256  There are several JavaScript SHA-256 implementations   I wrote tests to compare several hash implementations  see https   github com brillout test-javascript-hash-implementations   Or go to http   brillout github io test-javascript-hash-implementations   to run the tests

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I needed a similar function  but different  to generate a unique-ish ID based on the username and current time  So    window newId   - gt      create a number based on the username   unless window userNumber      window userNumber   0   for c i in window MyNamespace userName     char   window MyNamespace userName charCodeAt i      window MyNamespace userNumber  char     window MyNamespace userNumber   Math floor Math random     1e15    new Date   getMilliseconds    toString 36   toUpperCase     Produces    2DVFXJGEKL 6IZPAKFQFL ORGOENVMG     etc    edit Jun 2015  For new code I use shortid  https   www npmjs com package shortid

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If it helps anyone  I combined the top two answers into an older-browser-tolerant version  which uses the fast version if reduce is available and falls back to esmiralha s solution if it s not           see http   stackoverflow com q 7616461 940217     return  number      String prototype hashCode   function        if  Array prototype reduce           return this split     reduce function a b  a   a lt  lt 5 -a  b charCodeAt 0  return a amp a  0                            var hash   0      if  this length     0  return hash      for  var i   0  i  lt  this length  i              var character    this charCodeAt i           hash      hash lt  lt 5 -hash  character          hash   hash  amp  hash     Convert to 32bit integer           return hash      Usage is like   var hash    some string to be hashed  hashCode

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I m a bit surprised nobody has talked about the new SubtleCrypto API yet   To get an hash from a string  you can use the subtle digest method      x000D   x000D  function getHash str  algo    SHA-256     x000D    let strBuf   new TextEncoder  utf-8   encode str   x000D    return crypto subtle digest algo  strBuf  x000D       then hash   gt    x000D        window hash   hash  x000D           here hash is an arrayBuffer   x000D           so we ll connvert it to its hex version x000D        let result       x000D        const view   new DataView hash   x000D        for  let i   0  i  lt  hash byteLength  i    4    x000D          result      00000000    view getUint32 i  toString 16   slice -8   x000D          x000D        return result  x000D          x000D    x000D   x000D  getHash  hello world   x000D     then hash   gt    x000D      console log hash   x000D        x000D   x000D   x000D

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This generates a consistent hash based on any number of params passed in         Generates a hash from params passed in     returns  string  hash based on params     function fastHashParams         var args   Array prototype slice call arguments  join           var hash   0      if  args length    0            return hash            for  var i   0  i  lt  args length  i              var char   args charCodeAt i           hash     hash  lt  lt  5  - hash    char          hash   hash  amp  hash     Convert to 32bit integer           return String hash      fastHashParams  hello world   outputs  quot 990433808 quot  fastHashParams  this  1  has   lots   of   params  true  outputs  quot 1465480334 quot

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Slightly simplified version of  esmiralha s answer   I don t override String in this version  since that could result in some undesired behaviour   function hashCode str        var hash   0      for  var i   0  i  lt  str length  i              hash        hash  lt  lt  5  - hash    str charCodeAt i              return hash

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Note  Even with the best 32-bit hash  collisions will occur sooner or later  The hash collision probablility can be calculated as   aproximated as   see here   This may be higher than intuition suggests  Assuming a 32-bit hash and k 10 000 items  a collision will occur with a probablility of 1 2   For 77 163 samples the probability becomes 50    calculator   I suggest a workaround at the bottom   In an answer to this question Which hashing algorithm is best for uniqueness and speed   Ian Boyd posted a good in depth analysis  In short  as I interpret it   he comes to the conclusion that Murmur is best  followed by FNV-1a  Java   s String hashCode   algorithm that esmiralha proposed seems to be a variant of DJB2   FNV-1a has a a better distribution than DJB2  but is slower DJB2 is faster than FNV-1a  but tends to yield more collisions MurmurHash3 is better and faster than DJB2 and FNV-1a  but the optimized implementation requires more lines of code than FNV and DJB2   Some benchmarks with large input strings here  http   jsperf com 32-bit-hash When short input strings are hashed  murmur s performance drops  relative to DJ2B and FNV-1a  http   jsperf com 32-bit-hash 3 So in general I would recommend murmur3  See here for a JavaScript implementation  https   github com garycourt murmurhash-js If input strings are short and performance is more important than distribution quality  use DJB2  as proposed by the accepted answer by esmiralha   If quality and small code size are more important than speed  I use this implementation of FNV-1a  based on this code          Calculate a 32 bit FNV-1a hash    Found here  https   gist github com vaiorabbit 5657561    Ref   http   isthe com chongo tech comp fnv         param  string  str the input value     param  boolean   asString false  set to true to return the hash value as         8-digit hex string instead of an integer     param  integer   seed  optionally pass the hash of the previous chunk     returns  integer   string      function hashFnv32a str  asString  seed          jshint bitwise false        var i  l          hval    seed     undefined    0x811c9dc5   seed       for  i   0  l   str length  i  lt  l  i              hval    str charCodeAt i           hval     hval  lt  lt  1     hval  lt  lt  4     hval  lt  lt  7     hval  lt  lt  8     hval  lt  lt  24             if  asString               Convert to 8 digit hex string         return   quot 0000000 quot     hval  gt  gt  gt  0  toString 16   substr -8             return hval  gt  gt  gt  0     Improve Collision Probability As explained here  we can extend the hash bit size using this trick  function hash64 str        var h1   hash32 str       returns 32 bit  as 8 byte hex string      return h1   hash32 h1   str       64 bit  as 16 byte hex string     Use it with care and don t expect too much though

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String prototype hashCode   function       var hash   0  i  chr    if  this length     0  return hash    for  i   0  i  lt  this length  i          chr     this charCodeAt i       hash      hash  lt  lt  5  - hash    chr      hash    0     Convert to 32bit integer       return hash      Source  http   werxltd com wp 2010 05 13 javascript-implementation-of-javas-string-hashcode-method

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This is a refined and better performing variant  String prototype hashCode   function         var hash   0  i   0  len   this length      while   i  lt  len             hash      hash  lt  lt  5  - hash   this charCodeAt i      lt  lt  0            return hash      This matches Java s implementation of the standard object hashCode   Here is also one that returns only positive hashcodes  String prototype hashcode   function         return  this hashCode     2147483647    1      And here is a matching one for Java that only returns positive hashcodes  public static long hashcode Object obj        return   long  obj hashCode      Integer MAX VALUE   1l     Enjoy  Without prototype  function hashCode str        var hash   0  i   0  len   str length      while   i  lt  len             hash      hash  lt  lt  5  - hash   str charCodeAt i      lt  lt  0            return hash

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A fast and concise one which was adapted from here   String prototype hashCode   function       var hash   5381  i   this length   while i      hash    hash   33    this charCodeAt --i    return hash  gt  gt  gt  0

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SubtleCrypto digest     I   m not utilizing a server-side language so I can   t do it that way    Are you sure you can   t do it that way   Did you forget you   re using Javascript  the language ever-evolving   Try SubtleCrypto  It supports SHA-1  SHA-128  SHA-256  and SHA-512 hash functions      x000D   x000D  async function hash message    string       x000D   const text encoder   new TextEncoder  x000D   const data   text encoder encode message   x000D   const message digest   await window crypto subtle digest  SHA-512   data   x000D   return message digest  x000D       - gt  ArrayBuffer x000D   x000D  function in hex data    ArrayBuffer       x000D   const octets   new Uint8Array data   x000D   const hex      map call octets  octet   gt  octet toString 16  padStart 2   0    join      x000D   return hex  x000D       - gt  string x000D   x000D   async function demo     x000D   console log in hex await hash  Thanks for the magic       x000D        x000D   x000D   x000D

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This should be a bit more secure hash than some other answers  but in a function  without any preloaded source    I created basicly a minified simplified version of sha1  You take the bytes of the string and group them by 4 to 32bit  words  Then we extend every 8 words to 40 words  for bigger impact on the result   This goes to the hashing function  the last reduce  where we do some maths with the current state and the input  We always get 4 words out  This is almost a one-command one-line version using map reduce    instead of loops  but it is still pretty fast  String prototype hash   function        var rot    word  shift    gt  word  lt  lt  shift   word  gt  gt  gt   32 - shift       return unescape encodeURIComponent this valueOf     split     map char   gt              char charCodeAt 0            reduce  done  byte  idx  arr    gt              idx   4    0       done  arr slice idx  idx   4     done               reduce  done  group    gt                  done  group 0   lt  lt  24   group 1   lt  lt  16   group 2   lt  lt  8   group 3                 reduce  done  word  idx  arr    gt              idx   8    0       done  arr slice idx  idx   8     done               map group   gt                while group length  lt  40                  group push rot group group length - 2    group group length - 5    group group length - 8   3                return group             flat   reduce  state  word  idx  arr    gt                var temp     state 0    rot state 1   5    word   idx   state 3    amp  0xffffffff    state idx   2    0   4   5  state 0   state 1   state 2                state 0    rot state 1    state 2   11               state 1     state 2    rot  state 3   19               state 2    rot  state 3   11               state 3    temp              return state              0xbd173622  0x96d8975c  0x3a6d1a23  0xe5843775               w1  w2  w3    gt   w1  amp  rot w2  5       rot w1  11   amp  w3                w1  w2  w3    gt  w1   rot w2  5    rot w3  11             slice 0  4  map p   gt              p  gt  gt  gt  0           map word   gt                0000000    word toString 16   slice -8            join           we also convert the output to hex to get a string instead of word array  Usage is simple  for expample  a string  hash   will return  88a09e8f9cc6f8c71c4497fbb36f84cd    x000D   x000D  String prototype hash   function    x000D   var rot    word  shift    gt  word  lt  lt  shift   word  gt  gt  gt   32 - shift   x000D   return unescape encodeURIComponent this valueOf     split     map char   gt  x000D     char charCodeAt 0  x000D      reduce  done  byte  idx  arr    gt  x000D     idx   4    0       done  arr slice idx  idx   4     done x000D          reduce  done  group    gt  x000D         done  group 0   lt  lt  24   group 1   lt  lt  16   group 2   lt  lt  8   group 3   x000D          reduce  done  word  idx  arr    gt  x000D     idx   8    0       done  arr slice idx  idx   8     done x000D          map group   gt    x000D     while group length  lt  40  x000D      group push rot group group length - 2    group group length - 5    group group length - 8   3    x000D     return group  x000D       flat   reduce  state  word  idx  arr    gt    x000D     var temp     state 0    rot state 1   5    word   idx   state 3    amp  0xffffffff    state idx   2    0   4   5  state 0   state 1   state 2    x000D     state 0    rot state 1    state 2   11   x000D     state 1     state 2    rot  state 3   19   x000D     state 2    rot  state 3   11   x000D     state 3    temp  x000D     return state  x000D        0xbd173622  0x96d8975c  0x3a6d1a23  0xe5843775  x000D      w1  w2  w3    gt   w1  amp  rot w2  5       rot w1  11   amp  w3   x000D      w1  w2  w3    gt  w1   rot w2  5    rot w3  11   x000D      slice 0  4  map p   gt  x000D     p  gt  gt  gt  0 x000D      map word   gt  x000D       0000000    word toString 16   slice -8  x000D      join      x000D     x000D  let str    the string could even by empty   x000D  console log str hash     9f9aeca899367572b875b51be0d566b5 x000D   x000D   x000D

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Thanks to the example by mar10  I found a way to get the same results in C  AND Javascript for an FNV-1a  If unicode chars are present  the upper portion is discarded for the sake of performance  Don t know why it would be helpful to maintain those when hashing  as am only hashing url paths for now   C  Version  private static readonly UInt32 FNV OFFSET 32   0x811c9dc5       2166136261 private static readonly UInt32 FNV PRIME 32   0x1000193         16777619     Unsigned 32bit integer FNV-1a public static UInt32 HashFnv32u this string s           byte   arr   Encoding UTF8 GetBytes s           8 bit expanded unicode array     char   arr   s ToCharArray                         16 bit unicode is native  net       UInt32 hash   FNV OFFSET 32      for  var i   0  i  lt  s Length  i                     Strips unicode bits  only the lower 8 bits of the values are used         hash   hash   unchecked  byte  arr i   amp  0xFF            hash   hash   FNV PRIME 32            return hash        Signed hash for storing in SQL Server public static Int32 HashFnv32s this string s        return unchecked  int s HashFnv32u         JavaScript Version  var utils   utils         utils FNV OFFSET 32   0x811c9dc5   utils hashFnv32a   function  input        var hval   utils FNV OFFSET 32          Strips unicode bits  only the lower 8 bits of the values are used     for  var i   0  i  lt  input length  i              hval   hval    input charCodeAt i   amp  0xFF           hval     hval  lt  lt  1     hval  lt  lt  4     hval  lt  lt  7     hval  lt  lt  8     hval  lt  lt  24              return hval  gt  gt  gt  0     utils toHex   function  val        return   0000000     val  gt  gt  gt  0  toString 16   substr -8

[javascript] Generate a Hash from string in Javascript

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