web3.utils.toWei(web3.utils.fromWei(...))

Question

Is it warranted that web3.utils.toWei(web3.utils.fromWei(x)) is equal in numeric value to x (provided that x is a 256 bit number represented as a string)?

If it is not warranted, how to obtain a value not less (maybe a little greater) that x knowing web3.utils.fromWei(x)?

Answer 1

The experiment (takes like 15 sec on my i5 processor)

for(let i=0; i<1000000; ++i) {
  x = web3.utils.randomHex(32);
  if(x.replace(/x0*/, "x") !=  web3.utils.toHex(web3.utils.toWei(web3.utils.fromWei(x)))) {
    console.log(x);
    break;
  }
}

shows that in this case rounding errors do not happen.