Extract and list up function ids from opcodes.
npm install abi-decode-functions
```
$ npm install --save abi-decode-functions
```
const AbiFunctions = require('abi-decode-functions')
// or
// import AbiFunctions from 'abi-decode-functions'
const opcodes = getContractOpcodes()
const decoder = new AbiFunctions(opcodes)
const functionIds = dcoder.getFunctionIds()