function encode(int,encoding=256,signed){
  let size=2n**BigInt(encoding)
  let toReturn=null, filling="", sign=""
  if(typeof int!=="bigint"){int=BigInt(int)}
  
  //determining the binary string value
  if(int.toString()[0]==="-"){
    signed?sign=1:null //change sign from empty string to 1(meaning negative) if a signed bit, else do nothing
    toReturn=(size-(int%size)).toString(2)
  }
  else{
    signed?sign=0:null //change sign from empty string to 0(meaning positive) if a signed bit, else do nothing
    toReturn=(int%size).toString(2)
  }
  
  //to fill the spaces of empty bits
  let length=encoding-toReturn.length
  for(let i=0;i<length;i++){filling+=0}
  
  return sign+filling+toReturn //returns a String of 1s and 0s representing a binary encoded number
}

function decode(string,signed){ //returns a BigInt of the encoded string's value
  return signed?
  -1n*BigInt("0b"+string.substr(1)): //the signed translation
  BigInt("0b"+string) //the unsigned translation
}

console.log(encode(42)) //unsigned binary 256 bit of normal number
console.log(encode(4213213283721893738293789312731893n)) //unsigned binary 256 bit of a BigInt
console.log(encode("21157920892373161954235709850086879078532699846656405640394575840079131296399362")) //unsigned binary 256 bit of number larger than 2**256
console.log(encode("-21157920892373161954235709850086879078532699846656405640394575840079131296399362",128)) //unsigned binary 128 bit of number larger than 2**128
console.log(encode("-21157920892373161954235709850086879078532699846656405640394575840079131296399362",128,true)) //signed binary 128 bit of number larger than 2**128

console.log(decode( //unsigned encoded string DECODED
  encode(4213213283721893738293789312731893n)
))
console.log(decode( //signed encoded string DECODED
  encode(-4213213283721893738293789312731893n),true
))