abi-codec

Ethereum Contract ABI codec. Encodes function input and output according to provided contract ABI.

The purpose of this is library is to simplify working directly with JSON RPC methods such as eth_call and eth_sendTransaction.

Based on web3-eth-abi.

Install

npm install abi-codec
yarn add abi-codec

Methods

encodeInput

Parameters

• jsonInterface - Object: Contract JSON interface
• method - String: Method name
• params - Array: Parameters to encode

Returns

• String: Encoded input

decodeOutput

Parameters

• jsonInterface - Object: Contract JSON interface
• method - String: Method name
• output - String: Bytes to decode

Returns

• Array: Decoded output

Usage

// Example using an abbreviated JSON interface for the ENS registrar contract

const { encodeInput, decodeOutput } = require('abi-codec')

const jsonInterface = [
  {
    "constant": true,
    "inputs": [
      {
        "name": "node",
        "type": "bytes32"
      }
    ],
    "name": "resolver",
    "outputs": [
      {
        "name": "",
        "type": "address"
      }
    ]
  }
  ...
]

// Encode input for JSON RPC method `eth_call`
const namehash = '0x78c5b99cf4668cf6da387866de4331c78b75b7db0087988c552f73e1714447b9' // 32 byte name hash for 'ethereum.eth'
encodeInput(jsonInterface, 'resolver', [namehash])
// -> '0x0178b8bf78c5b99cf4668cf6da387866de4331c78b75b7db0087988c552f73e1714447b9'

// Decode output from JSON RPC method `eth_call`
const output = '0x0178b8bf78c5b99cf4668cf6da387866de4331c78b75b7db0087988c552f73e1714447b9'
decodeOutput(jsonInterface, 'resolver', output)
// -> [ '0x1da022710dF5002339274AaDEe8D58218e9D6AB5' ]