anshuman-singh-93

// user.controller.js

const { UserError } = require('./util')

const saveUser = async ({ body } = {}) => {
  if (!body.name) {
    throw new UserError('name field is missing',400); // operational error
  }

  let result1 =  await saveUserInDB(body);

anshuman-singh-93

// user.route.js
const express = require('express');
const router = express.Router();
const { saveUser } = require('./user.controller');
const { Helper } = require('./util');

router.post('/', Helper.requestHandler.call(null,saveUser));
// exporting router object to main file where we have app object
module.exports = router;

anshuman-singh-93

// user.route.js
const express = require('express');
const router = express.Router();
const { saveUser } = require('./user.controller');
router.post('/', saveUser);
// exporting router object to main file where we have app object
module.exports = router;

anshuman-singh-93

class UserError extends Error {

    constructor(message, statusCode) {
        super(message)
        this.name = this.constructor.name;
        this.statusCode = statusCode;
        Error.captureStackTrace(this, UserError)

    }
}

anshuman-singh-93

const saveUser = async (req, res) => {
  let { body } = req;
  let result1, result2;
  if (typeof body !== 'object') {
    return res.status(400).json({ message: 'data must be an object' })
  }

  try {
    result1 = await saveUserInDB(body);
  }

anshuman-singh-93

const promisifyIt = (fn) => (...args)=>{
  return new Promise((resolve,reject)=>{
    fn(...args,(err,data)=>{
      if(err){
        reject(err)
      }
      else{
        resolve(data)
      }
    })

anshuman-singh-93

0x45bef9Be3B4B43e674a2A8A0E9375867A1718CC7

anshuman-singh-93

0xC01af13d073E6eb9c2e4B6CBC789F3f02f9F9CD6

anshuman-singh-93

/**
 * Fancy ID generator that creates 20-character string identifiers with the following properties:
 *
 * 1. They're based on timestamp so that they sort *after* any existing ids.
 * 2. They contain 72-bits of random data after the timestamp so that IDs won't collide with other clients' IDs.
 * 3. They sort *lexicographically* (so the timestamp is converted to characters that will sort properly).
 * 4. They're monotonically increasing.  Even if you generate more than one in the same timestamp, the
 *    latter ones will sort after the former ones.  We do this by using the previous random bits
 *    but "incrementing" them by 1 (only in the case of a timestamp collision).
 */

anshuman-singh-93

Latency Comparison Numbers
--------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD