How to store a byte array in Javascript

Question

I m going to be storing a large array of byte values  most likely over a million  in Javascript  If I use a normal array with normal numbers  that will take 8 MB  because numbers are stored as IEEE doubles  but if I can store it as bytes  it will be only 1 MB   I d like to avoid wasting that much space for obvious reasons  Is there a way to store bytes as bytes instead of doubles  Browser compatibility isn t an issue for me  as long as it works in Chrome  This is in HTML5  if that makes a difference

User · Answer

var array   new Uint8Array 100       array 10    256  array 10      0    true   I verified in firefox and chrome  its really an array of bytes    var array   new Uint8Array 1024 1024 50       allocates 50MBytes

User · Answer

By using typed arrays  you can store arrays of these types    Int8 Uint8 Int16 Uint16 Int32 Uint32 Float32 Float64   For example    var array   new Uint8Array 100   array 42    10  alert array 42       See it in action here

User · Answer

I wanted a more exact and useful answer to this question  Here s the real answer  adjust accordingly if you want a byte array specifically  obviously the math will be off by a factor of 8 bits   1 byte    class BitArray     constructor bits   0        this uints   new Uint32Array    bits   32           getBit bit        return  this uints    bit   32    amp   1  lt  lt   bit   32       0   1   0         assignBit bit  value        if  value          this uints    bit   32       1  lt  lt   bit   32          else         this uints    bit   32    amp     1  lt  lt   bit   32                 get size         return this uints length   32         static bitsToUints bits        return    bits   32           Usage   let bits   new BitArray 500   for  let uint   0  uint  lt  bits uints length    uint      bits uints uint    457345834    for  let bit   0  bit  lt  50    bit      bits assignBit bit  1     str       for  let bit   bits size - 1  bit  gt   0  --bit      str    bits getBit bit     str    Output    00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000101000101100101010  00011011010000111111111111111111  11111111111111111111111111111111    Note  This class is really slow to e g  assign bits  i e   2s per 10 million assignments  if it s created as a global variable  at least in the Firefox 76 0 Console on Linux    If  on the other hand  it s created as a variable  i e  let bits   new BitArray 1e7     then it s blazingly fast  i e   300ms per 10 million assignments      For more info  see here     How do you set  clear and toggle a single bit in JavaScript    https   stackoverflow com a 1436448 1599699 https   developer mozilla org en-US docs Web JavaScript Reference Operators Bitwise Operators https   developer mozilla org en-US docs Web JavaScript Typed arrays https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Uint32Array   Note that I used Uint32Array because there s no way to directly have a bit byte array  that you can interact with directly  and because even though there s a BigUint64Array  JS only supports 32 bits      Bitwise operators treat their operands as a sequence of 32 bits               The operands of all bitwise operators are converted to   32-bit integers

User · Answer

You could store the data in an array of strings of some large fixed size   It should be efficient to access any particular character in that array of strings  and to treat that character as a byte   It would be interesting to see the operations you want to support  perhaps expressed as an interface  to make the question more concrete

[javascript] How to store a byte array in Javascript

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