是否可以使用web3.js从Solidity获取uint256值

Question

So the question is pretty simple. I am calling contract method that returns uint256 value. Is it possible to get that value in JavaScript at all? As far as I understand JavaScript can't work with big numbers and the solution would be to make new contract that returns data as string? Right now I am getting a value that simply cuts a lot of zeros :)

Answer 1

Web3 returns primitive data types (including uint ) as strings. If you try to parse it into javascript native number with something like parseInt , it will fail.

To work with the big numbers received via web3, you have to use library which can handle them. One such library is BigNumber.JS https://github.com/MikeMcl/bignumber.js/

So you can then use it like this:

let result = BigNumber(await bigNumber.methods.getNum1().call());

and use math operations implemented by BigNumber.js

result = result.plus("99999999999999999999999999999999999999");

note that if you then simply try to use the result value itself

console.log(result);

you will get result like this

  BigNumber {
    s: 1,
    e: 38,
    c: [ 10000000213, 12312312312312, 45465777775431 ] }

Therefore you will probably want to cast it to the string in the end

console.log(result.toString());

to get result in readable form, like:

1.00000002131231231231231245465777775431e+38