How do I get a JSON-RPC quantity value?

[einaralex]

Describe the bug
When trying to translate the chainId of Polygon test network (Mumbai) to hex with utils.hexlify(80001), the outcome is wrong. It should be 0x13881 but returns 0x013881.

Reproduction steps

import {  utils } from 'ethers';
console.log(utils.hexlify(80001));

Search Terms
hexlify, polygon, chainId, Mumbai

[ricmoo]

The hexlify function returns the bytes representation, which means it will be of even length and can be safely used to interchange the two formats without having to understand the padding operation to reverse the process (bytes, which pad the right, vs numeric, which pads the left).

You want to use the utils.hexValue function to compute the “quantity” type, used commonly in the Ethereum JSON-RPC API.