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)] & (1 << (bit % 32))) != 0 ? 1 : 0;
}
assignBit(bit, value) {
if (value) {
this.uints[~~(bit / 32)] |= (1 << (bit % 32));
} else {
this.uints[~~(bit / 32)] &= ~(1 << (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 < bits.uints.length; ++uint) {
bits.uints[uint] = 457345834;
}
for (let bit = 0; bit < 50; ++bit) {
bits.assignBit(bit, 1);
}
str = '';
for (let bit = bits.size - 1; bit >= 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:
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