BigInt and Unit-Handling

Numbers in smart contracts are usually stored without decimals as big numbers, and a second variable contains information about the amount of decimals.

Some utility functions can help ease the handling of these numbers, especially with the bigint support now being natively available:

Convert Token Balance to Human-Readable Version

For example, reading the balance of VTHO and turning it into a readable version:

import { ThorClient, Contract } from '@vechain/sdk-network';
const thor = ThorClient.fromUrl('https://mainnet.vechain.org');

const contract = new Contract('0x0000000000000000000000000000456e65726779', [
  'function balanceOf(address _owner) returns (uint256)',
  'function decimals() returns (uint256)',
]);

const [[balance], [decimals]] = await thor.contracts.executeMultipleClausesCall(
  [
    contract.clause.balanceOf('0x0000000000000000000000000000000000000000'),
    contract.clause.decimals(),
  ]
);
console.log(balance, decimals, '=>', unitsUtils.formatUnits(balance, decimals));

Using unitsUtils.formatUnits(number, decimals), the number is turned into a string with the decimal right where a human needs it.

Convert Human Inputs to BigInts

When building user interfaces, numbers are entered as strings and need to be turned into BigInts for interaction with the blockchain.

unitsUtils.parseUnits(string, decimals) helps in that way. For example:

unitsUtils.parseUnits('5', 18)   // => turns into 5000000000000000000n
unitsUtils.parseUnits('0.1', 18) // => turns into 100000000000000000n