Isomorphic-Rpc

A (promise based) Javascript wrapper for clean JSON-RPC method calls

What is JSON-RPC

A standard format for HTTP requests (much like REST), that is used by most cryptocurrency servers.

For Example

For instance a curl request like this:

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["latest",false],"id":1}' -H "Content-type:application/json" https://www.ethercluster.com/etc

Can be executed in javascript like this:

rpc.eth_getBlockByNumber("latest", false).then(console.log) see initialization steps below

In general this should support any JSON-RPC application, but I made it to simplify my ethereum applications and I've only used/tested it on the same.

Use in place of Web3

• because web3 is huge
• web3 doesn't follow the spec (i.e. spec has eth_getBlockByHash, web3 has only getBlock)
• web3 randomly prints some values as hex string ("0x1234") while others come back as number and for some odd reason block.difficulty is returned as a string of decimal digits (lol WAHT?)
• New RPC methods like getProof are not supported (in web3 or other libraries) until each piece of software in the chain publishes a feature update to support it.

Solution

Using Ecmascript's new Proxy functionality you can create an object such that when you call a missing method on it, it instead calls a "handler" function that has access to the method name called.

The library uses this to automatically create an RPC request from any method name given. So any brand new or experimental RPC method your client software supports will be exposed.

Extremely Lightweight

The module is 37 lines of code. There is only 1 dependency (which branches into 3 small packages). It's only there to enables the library to be isomorphic.

Isomorphism

The use of this library should work identically in both Node and all desktop/mobile Browsers (except Internet Explorer because bill gates is busy curing malaria)

Use

npm install isomorphic-rpc

const Rpc = require('isomorphic-rpc')
let rpc = new Rpc('https://www.ethercluster.com/etc') // or default to "http://localhost:8545"
// or  "https://mainnet.infura.io" or even "https://web3.gastracker.io" etc...
rpc.web3_sha3("0x").then(console.log)

rpc.eth_getBlockByNumber("latest", false).then(console.log)

or within an async function:

let hash = await rpc.web3_sha3("0x")

Docs

The JSON-RPC Page is the most up to date list of supported Ethereum RPC calls.

Also the RPC 2.0 Specification could be useful in updating this package. If a PR will help it better supports the RPC spec, I'll merge it in.