Add JSON serializability to BigNumber

[briarsweetbriar]

I was expecting this:

ethers.utils.bigNumberify(JSON.parse(JSON.stringify(ethers.utils.bigNumberify("1"))))

to generate a BigNumber. Instead, it throws:

Uncaught Error: invalid BigNumber value (arg="value", value={"_hex":"0x01"})
at Object.throwError (ethers.js:13663)
at new BigNumber (ethers.js:13213)
at Object.bigNumberify (ethers.js:13290)
at :1:14

When I:

JSON.parse(JSON.stringify(ethers.utils.bigNumberify("1")))

the result is:

{_hex: "0x01"}

where as:

ethers.utils.bigNumberify("1")

returns:

{_hex: "0x01", _ethersType: "BigNumber"}

so it looks like JSON.stringify is losing the _ethersType, which is preventing ethers.utils.bigNumberify from correctly parsing it.

[ricmoo]

A BigNumber is a complex type which, in general, cannot be serialized using JSON. For example, in JavaScript this also does not work:

> new RegExp(JSON.parse(JSON.stringify(new RegExp(/Hello/))))
/[object Object]/

To serialize and deserialize a BigNumber, the hex is probably the easiest thing to use:

let serialized = value.toHexString();

let deserialized = ethers.utils.bigNumberify(serialized);

That said, supporting the behaviour you have above seems useful, and fairly easy (+ safe) to add. I will leave this ticket open as an enhancement for the library and get to it soon.

Thanks!

[briarsweetbriar]

Thank you!

[ricmoo]

This has been added in 4.0.2.

Let me know if you have any issues with it.

Thanks! :)

[iradofurioso]

bigNumberify

bigNumberify didn't work (threw an error) but BigNumber.from did the job.
in case anyone wats to convert to real value to print on screen: ethers.utils.formatEther

[TrejGun]

just in case

import { BigNumber } from "ethers";

Object.defineProperties(BigNumber.prototype, {
  toJSON: {
    value: function (this: BigNumber) {
      return this.toString();
    },
  },
});

console.log(JSON.stringify(BigNumber.from("1"))); // "1"