A Node.js JSON-RPC client

example.js

const { createClient } = require('./JsonRpcClient')

;(async () => {
  const client = createClient('node.supportxmr.com', 18081)
  const { height } = await client.getInfo()
  console.log('The last block height was %d.', height)
})()

JsonRpcClient.js

/*
 * JsonRpcClient.js 1.0 - A Node.js JSON-RPC client
 *
 * Written in 2019 by Matt Smith <matt@offtopica.uk>
 *
 * To the extent possible under law, the author(s) have dedicated all
 * copyright and related and neighboring rights to this software to
 * the public domain worldwide. This software is distributed without
 * any warranty.
 *
 * See https://creativecommons.org/publicdomain/zero/1.0/ for more
 * info.
 */

const http = require('http')

const JSONRPC = '2.0'

class JsonRpcClient {
  constructor (hostname, port, path = '/json_rpc') {
    this._agent = new http.Agent({ keepAlive: true })
    this._hostname = hostname
    this._path = path
    this._port = port
  }

  call (method, params = {}) {
    return new Promise((resolve, reject) => {
      const payload = JSON.stringify({
        jsonrpc: JSONRPC,
        id: '0',
        method,
        params
      })

      const options = {
        agent: this._agent,
        hostname: this._hostname,
        port: this._port,
        path: this._path,
        method: 'POST',
        headers: {
          'Content-Length': Buffer.byteLength(payload),
          'Content-Type': 'application/json'
        }
      }

      const req = http.request(options, res => {
        let response = ''

        res.setEncoding('utf8')

        res.on('data', chunk => {
          response += chunk
        })

        res.on('end', () => {
          try {
            const decoded = JSON.parse(response)
            if (decoded.error) {
              return reject(new Error(decoded.error.message))
            } else if (decoded.result) {
              return resolve(decoded.result)
            } else {
              return reject(new Error('Malformed response'))
            }
          } catch (err) {
            reject(err)
          }
        })
      })

      req.on('error', err => { return reject(err) })

      req.write(payload)
      req.end()
    })
  }
}

const snakeCase = x =>
  x.replace(/([a-z])([A-Z])/g, '$1_$2').toLowerCase()

const createClient = (hostname, port, path) =>
  new Proxy(new JsonRpcClient(hostname, port, path), {
    get: (target, prop) =>
      target[prop]
        ? target[prop]
        : params => target.call(snakeCase(prop), params)
  })

module.exports = { createClient }