intToDecimal.js

const BN = require('bn.js');

const stripHexPrefix = val => typeof val === 'string' && val.indexOf('0x') === 0 ? val.slice(2) : val;
const hexPrefix = val => val ? (`0x${stripHexPrefix((val || {}).div ? val.toString(16) : val)}`) : val;
const hexToBN = val => (val || {}).div ? val : new BN(stripHexPrefix(hexPrefix(val)), 16);
const numToBN = val => (val || {}).div || String(val).indexOf('0x') !== -1 ? hexToBN(val) : new BN(val, 10);

function intToDecimal(weiInput, baseLength, optionsInput) {
  var wei = numToBN(weiInput); // eslint-disable-line
  var negative = wei.lt(new BN(0)); // eslint-disable-line
  const base = (new BN(10, 10)).pow(numToBN(baseLength));
  const options = optionsInput || {};

  if (negative) {
    wei = wei.mul(new BN(-1));
  }

  var fraction = wei.mod(base).toString(10); // eslint-disable-line

  while (fraction.length < baseLength) {
    fraction = `0${fraction}`;
  }

  if (!options.pad) {
    fraction = fraction.match(/^([0-9]*[1-9]|0)(0*)/)[1];
  }

  var whole = wei.div(base).toString(10); // eslint-disable-line

  if (options.commify) {
    whole = whole.replace(/\B(?=(\d{3})+(?!\d))/g, ',');
  }

  var value = `${whole}${fraction == '0' ? '' : `.${fraction}`}`; // eslint-disable-line

  if (negative) {
    value = `-${value}`;
  }

  return value;
}