How to convert uint8 Array to base64 Encoded String

Question

I got a webSocket comunication  I recieve base64 encoded string  convert it to uint8 and work on it  but now I need to send back  I got the uint8 array  and need to convert it to base64 string  so I can send it  How can I make this convertion

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function Uint8ToBase64 u8Arr     var CHUNK SIZE   0x8000    arbitrary number   var index   0    var length   u8Arr length    var result         var slice    while  index  lt  length        slice   u8Arr subarray index  Math min index   CHUNK SIZE  length         result    String fromCharCode apply null  slice       index    CHUNK SIZE        return btoa result       You can use this function if you have a very large Uint8Array  This is for Javascript  can be useful in case of FileReader readAsArrayBuffer

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npm install google-closure-library --save  require  google-closure-library    goog require  goog crypt base64     var result  goog crypt base64 encodeByteArray Uint8Array of 1 83 27 99 102 66    console log result      node index js would write AVMbY2Y  to the console

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Use the following to convert uint8 array to base64 encoded string function arrayBufferToBase64 buffer                var binary                   var bytes      slice call new Uint8Array buffer                bytes forEach  b    gt  binary    String fromCharCode b                return window btoa binary

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See here https   developer mozilla org en-US docs Web JavaScript Base64 encoding and decoding Appendix 3A Decode a Base64 string to Uint8Array or ArrayBuffer   Decode a Base64 string to Uint8Array or ArrayBuffer with Unicode support

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To base64-encode a UInt8Array with arbitrary data  not necessarily UTF-8  using native browser functionality  const base64 arraybuffer   async  data    gt           Use a FileReader to generate a base64 data URI     const base64url   await new Promise  r    gt            const reader   new FileReader           reader onload        gt  r reader result          reader readAsDataURL new Blob  data                       The result looks like       quot data application octet-stream base64  lt your base64 data gt  quot        so we split off the beginning             return base64url split  quot   quot   2  1        example use  await base64 arraybuffer new UInt8Array  1 2 3 100 200

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If your data may contain multi-byte sequences  not a plain ASCII sequence  and your browser has TextDecoder  then you should use that to decode your data  specify the required encoding for the TextDecoder    var u8   new Uint8Array  65  66  67  68    var decoder   new TextDecoder  utf8    var b64encoded   btoa decoder decode u8      If you need to support browsers that do not have TextDecoder  currently just IE and Edge   then the best option is to use a TextDecoder polyfill   If your data contains plain ASCII  not multibyte Unicode UTF-8  then there is a simple alternative using String fromCharCode that should be fairly universally supported   var ascii   new Uint8Array  65  66  67  68    var b64encoded   btoa String fromCharCode apply null  ascii      And to decode the base64 string back to a Uint8Array   var u8 2   new Uint8Array atob b64encoded  split     map function c        return c charCodeAt 0          If you have very large array buffers then the apply may fail and you may need to chunk the buffer  based on the one posted by  RohitSengar   Again  note that this is only correct if your buffer only contains non-multibyte ASCII characters   function Uint8ToString u8a     var CHUNK SZ   0x8000    var c         for  var i 0  i  lt  u8a length  i  CHUNK SZ        c push String fromCharCode apply null  u8a subarray i  i CHUNK SZ           return c join           Usage var u8   new Uint8Array  65  66  67  68    var b64encoded   btoa Uint8ToString u8

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Pure JS - no string middlestep  no btoa  In below solution I omit conversion to string  IDEA is following   join 3 bytes  3 array elements  and you get 24-bits split 24bits to four 6-bit numbers  which take values from 0 to 63  use that numbers as index in base64 alphabet corner case  when input byte array the length is not divided by 3 then add   or    to result  Solution below works on 3-bytes chunks so it is good for large arrays  Similar solution to convert base64 to binary array  without atob  is HERE  x000D   x000D  function bytesArrToBase64 arr      const abc    ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789        base64 alphabet   const bin   n   gt  n toString 2  padStart 8 0      convert num to 8-bit binary string   const l   arr length   let result          for let i 0  i lt   l-1  3  i          let c1   i 3 1 gt  l     case when     is on end     let c2   i 3 2 gt  l     case when     is on end     let chunk   bin arr 3 i     bin c1  0 arr 3 i 1     bin c2  0 arr 3 i 2        let r   chunk match    1 6  g  map  x j   gt  j  3 amp  amp c2         j  2 amp  amp c1       abc    0b  x            result    r join             return result         ----------    TEST    ----------  let test    Alice s Adventure in Wondeland    let testBytes       test  map c  gt  c charCodeAt 0      console log  test string    test   console log  bytes    JSON stringify testBytes    console log  btoa               btoa test    console log  bytesArrToBase64   bytesArrToBase64 testBytes    x000D   x000D   x000D

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If you are using Node js then you can use this code to convert Uint8Array to base64  var b64   Buffer from u8  toString  base64

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Very simple solution and test for JavaScript   ToBase64   function  u8        return btoa String fromCharCode apply null  u8       FromBase64   function  str        return atob str  split     map function  c    return c charCodeAt 0          var u8   new Uint8Array 256   for  var i   0  i  lt  256  i        u8 i    i   var b64   ToBase64 u8   console debug b64   console debug FromBase64 b64

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All solutions already proposed have severe problems  Some solutions fail to work on large arrays  some provide wrong output  some throw an error on btoa call if an intermediate string contains multibyte characters  some consume more memory than needed   So I implemented a direct conversion function which just works regardless of the input  It converts about 5 million bytes per second on my machine   https   gist github com enepomnyaschih 72c423f727d395eeaa09697058238727   x000D   x000D     x000D  MIT License x000D  Copyright  c  2020 Egor Nepomnyaschih x000D  Permission is hereby granted  free of charge  to any person obtaining a copy x000D  of this software and associated documentation files  the  Software    to deal x000D  in the Software without restriction  including without limitation the rights x000D  to use  copy  modify  merge  publish  distribute  sublicense  and or sell x000D  copies of the Software  and to permit persons to whom the Software is x000D  furnished to do so  subject to the following conditions  x000D  The above copyright notice and this permission notice shall be included in all x000D  copies or substantial portions of the Software  x000D  THE SOFTWARE IS PROVIDED  AS IS   WITHOUT WARRANTY OF ANY KIND  EXPRESS OR x000D  IMPLIED  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY  x000D  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT  IN NO EVENT SHALL THE x000D  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM  DAMAGES OR OTHER x000D  LIABILITY  WHETHER IN AN ACTION OF CONTRACT  TORT OR OTHERWISE  ARISING FROM  x000D  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE x000D  SOFTWARE  x000D     x000D   x000D     x000D     This constant can also be computed with the following algorithm  x000D  const base64abc       x000D   A    A  charCodeAt 0   x000D   a    a  charCodeAt 0   x000D   n    0  charCodeAt 0   x000D  for  let i   0  i  lt  26    i    x000D   base64abc push String fromCharCode A   i    x000D    x000D  for  let i   0  i  lt  26    i    x000D   base64abc push String fromCharCode a   i    x000D    x000D  for  let i   0  i  lt  10    i    x000D   base64abc push String fromCharCode n   i    x000D    x000D  base64abc push       x000D  base64abc push       x000D     x000D  const base64abc     x000D    A    B    C    D    E    F    G    H    I    J    K    L    M   x000D    N    O    P    Q    R    S    T    U    V    W    X    Y    Z   x000D    a    b    c    d    e    f    g    h    i    j    k    l    m   x000D    n    o    p    q    r    s    t    u    v    w    x    y    z   x000D    0    1    2    3    4    5    6    7    8    9            x000D     x000D   x000D     x000D     This constant can also be computed with the following algorithm  x000D  const l   256  base64codes   new Uint8Array l   x000D  for  let i   0  i  lt  l    i    x000D   base64codes i    255     invalid character x000D    x000D  base64abc forEach  char  index    gt    x000D   base64codes char charCodeAt 0     index  x000D      x000D  base64codes     charCodeAt 0     0     ignored anyway  so we just need to prevent an error x000D     x000D  const base64codes     x000D   255  255  255  255  255  255  255  255  255  255  255  255  255  255  255  255  x000D   255  255  255  255  255  255  255  255  255  255  255  255  255  255  255  255  x000D   255  255  255  255  255  255  255  255  255  255  255  62  255  255  255  63  x000D   52  53  54  55  56  57  58  59  60  61  255  255  255  0  255  255  x000D   255  0  1  2  3  4  5  6  7  8  9  10  11  12  13  14  x000D   15  16  17  18  19  20  21  22  23  24  25  255  255  255  255  255  x000D   255  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  x000D   41  42  43  44  45  46  47  48  49  50  51 x000D     x000D   x000D  function getBase64Code charCode    x000D   if  charCode  gt   base64codes length    x000D    throw new Error  Unable to parse base64 string     x000D     x000D   const code   base64codes charCode   x000D   if  code     255    x000D    throw new Error  Unable to parse base64 string     x000D     x000D   return code  x000D    x000D   x000D  export function bytesToBase64 bytes    x000D   let result       i  l   bytes length  x000D   for  i   2  i  lt  l  i    3    x000D    result    base64abc bytes i - 2   gt  gt  2   x000D    result    base64abc   bytes i - 2   amp  0x03   lt  lt  4     bytes i - 1   gt  gt  4    x000D    result    base64abc   bytes i - 1   amp  0x0F   lt  lt  2     bytes i   gt  gt  6    x000D    result    base64abc bytes i   amp  0x3F   x000D     x000D   if  i     l   1       1 octet yet to write x000D    result    base64abc bytes i - 2   gt  gt  2   x000D    result    base64abc  bytes i - 2   amp  0x03   lt  lt  4   x000D    result          x000D     x000D   if  i     l       2 octets yet to write x000D    result    base64abc bytes i - 2   gt  gt  2   x000D    result    base64abc   bytes i - 2   amp  0x03   lt  lt  4     bytes i - 1   gt  gt  4    x000D    result    base64abc  bytes i - 1   amp  0x0F   lt  lt  2   x000D    result         x000D     x000D   return result  x000D    x000D   x000D  export function base64ToBytes str    x000D   if  str length   4     0    x000D    throw new Error  Unable to parse base64 string     x000D     x000D   const index   str indexOf       x000D   if  index     -1  amp  amp  index  lt  str length - 2    x000D    throw new Error  Unable to parse base64 string     x000D     x000D   let missingOctets   str endsWith         2   str endsWith        1   0  x000D    n   str length  x000D    result   new Uint8Array 3    n   4    x000D    buffer  x000D   for  let i   0  j   0  i  lt  n  i    4  j    3    x000D    buffer   x000D     getBase64Code str charCodeAt i    lt  lt  18   x000D     getBase64Code str charCodeAt i   1    lt  lt  12   x000D     getBase64Code str charCodeAt i   2    lt  lt  6   x000D     getBase64Code str charCodeAt i   3    x000D    result j    buffer  gt  gt  16  x000D    result j   1     buffer  gt  gt  8   amp  0xFF  x000D    result j   2    buffer  amp  0xFF  x000D     x000D   return result subarray 0  result length - missingOctets   x000D    x000D   x000D  export function base64encode str  encoder   new TextEncoder      x000D   return bytesToBase64 encoder encode str    x000D    x000D   x000D  export function base64decode str  decoder   new TextDecoder      x000D   return decoder decode base64ToBytes str    x000D    x000D   x000D   x000D

User · Answer

If all you want is a JS implementation of a base64-encoder  so that you can send data back  you can try the btoa function   b64enc   btoa uint     A couple of quick notes on btoa - it s non-standard  so browsers aren t forced to support it  However  most browsers do   The big ones  at least  atob is the opposite conversion   If you need a different implementation  or you find an edge-case where the browser has no idea what you re talking about  searching for a base64 encoder for JS wouldn t be too hard   I think there are 3 of them hanging around on my company s website  for some reason

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Here is a JS Function to this      This function is needed because Chrome doesn t accept a base64 encoded string   as value for applicationServerKey in pushManager subscribe yet   https   bugs chromium org p chromium issues detail id 802280   function urlBase64ToUint8Array base64String      var padding       repeat  4 - base64String length   4    4     var base64    base64String   padding       replace   - g            replace    g           var rawData   window atob base64     var outputArray   new Uint8Array rawData length      for  var i   0  i  lt  rawData length    i        outputArray i    rawData charCodeAt i         return outputArray

[javascript] How to convert uint8 Array to base64 Encoded String?

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