Eth Method Registry 
A javascript library for getting Solidity method data from a four-byte method signature.
Currently uses the parity on-chain method registry, but eventually I am interested in adding various parallel methods, whatever works and returns a valid response!
Installation
With Node.js Installed:
npm install eth-method-registry -S
Usage
const MethodRegistry = require('eth-method-registry')
const Eth = require('ethjs')
const provider = new Eth.HttpProvider('https://mainnet.infura.io')
const registry = new MethodRegistry({ provider })
// Uses promises, pass the 4byte prefix to the lookup method:
registry.lookup('0xa9059cbb')
.then((result) => {
assert.equal(result, 'transfer(address,uint256)', 'finds correct signature')
})
// Also includes a method for parsing the resulting sig
// into something more useful for rendering:
const sig = 'transferFrom(address,uint256)'
const parsed = registry.parse(sig)
/* Parsed value:
{
name :'Transfer From',
args: [
{ type: 'address' },
{ type: 'uint256' }
]
}
*/