NodeJS: RPC Client module class (either callback and async/await available)

example.js

const RpcClient = require("./RpcClient.js");
const rpcClient = new RpcClient({ url: "https://ropsten.infura.io/XXXXXXX" });

// RPC request param
const param = {
  method: "eth_getBalance",
  params: ["0x5724feec83cec20cc4392033ab2753dc8513e333", "latest"],
};

// callback way:
rpcClient.call(param, (err, res)=>{
  console.log("callback result:", err, res);
});

// async/await way:
(async() => {
  try {
    const result = await rpcClient.call(param);
    console.log("async/await result:", result);
  } catch(ex) {
    console.error(ex);
  }
})().catch(console.error);

RpcClient.js

// Simple JSON RPC Client
const request = require("request");
const requestAsync = require("request-promise");
// const axios = require("axios");

module.exports = class RpcClient {

  constructor({
    url,
    jsonrpc = "2.0",
    debug = false,
    logger = console,
  }) {
    if (!RpcClient.isValidUrl(url))
      throw Error(`invalid url: "${url}"`);
    this.url = url;
    this.jsonrpc = jsonrpc;
    this.debug = debug;
    this.logger = logger;
  }

  //**************************************************************
  // main methods
  //**************************************************************

  /**
   * RPC request. Either callback and async/await available
   * Example: `call({method:"getblockhash", params:["1"], id:1}, (err, res)=>{...});
   * @param {Object} - params:
   *  - method {String} - RPC method
   *  - params {Object} - RPC params
   *  - id {String|Number} - [Optional] RPC request ID
   *  - requestOpts {Object} - [Optional] request options.
   *    @see:https://github.com/request/request#requestoptions-callback
   */
  async call({ method, params, id = 1, requestOpts = {} }, cb) {
    const self = this;
    const p = self._createRequestParam(method, params, id, requestOpts);
    if (typeof cb === "function") { // callback
      request(p, (err, response, body) => {
        if (err) return cb && cb(err);
        return cb && cb(err, bodyToResult(body));
      });
    } else { // async/await
      const body = await requestAsync(p);
      return bodyToResult(body);
    }

    function bodyToResult(bodyStr) {
      try {
        const body = JSON.parse(bodyStr); // parse json string
        const err = (body && body.error) ? body.error : null;
        const result = (body && body.result) ? body.result : null;
        return result;
      } catch (ex) {
        return null;
      }
    }
  }

  //**************************************************************
  // sub methods
  //**************************************************************

  /**
   * Creates request parameter
   */
  _createRequestParam(method, params, id, requestOpts) {
    // RPC Param: looks like this:  '{"jsonrpc": "1.0", "id":"curltest", "method": "getinfo", "params": [] }'
    const data = {
      jsonrpc: this.jsonrpc,
      id,
      method,
      params,
    };
    let p = {
      url: this.url,
      body: JSON.stringify(data),
      headers: {
        "Content-type": "application/json; charset=UTF-8",
        "Accept": "application/json, text/javascript",
      },
      method: "POST", // JSONRPC server handles only POST requests
      encoding: "UTF-8",
      // json: true,
    };
    if (requestOpts) p = Object.assign(p, requestOpts);
    if (this.debug) this.logger.info("requesting param:", p);
    return p;
  }

  //**************************************************************
  // utility static methods
  //**************************************************************

  static isValidUrl(v) {
    return /^https?:\/\/.+$/.test(v);
  }

};