Node.js | Handy Snippets

Delayed Event Trigger

var timeoutId; // set to global or to any enclosing parent scope
// @params delay (milli seconds), customEvent (any function)
function delayedTrigger(delay, customEvent) {
    if(timeoutId) {
        clearTimeout(timeoutId);
    }
    timeoutId = setTimeout(()=> {
        customEvent()
    }, delay);  
}

// -- Test -- 
// The event is triggered only once even if called multiple times in succession.
// This is a critical performance optimization to avoid triggering multiple 
// calls to the underlying event.
for(var i = 0;i<3;i++) {
    delayedTrigger(2000, ()=>{
        console.log('Event Triggered')
    });
}

Create Dir If Not Exists

function createDirIfNotExists(newPath) {
  if (!fs.existsSync(newPath)) {
    fs.mkdirSync(newPath, { recursive: true });
  }
}

Gen asymmetric cryptography - Key Pair

JSON Web Token (JWT) — The right way of implementing, with Node.js

// ref: https://thomasstep.com/blog/a-guide-to-using-jwt-in-javascript
import { generateKeyPair } from 'jose';
import fs from 'fs'

async function genKeyPair() {
  try {
    const { publicKey, privateKey } = await generateKeyPair('RS256');
    // https://nodejs.org/api/crypto.html#crypto_class_keyobject
    const publicKeyString = publicKey.export({
      type: 'pkcs1',
      format: 'pem',
    });
    const privateKeyString = privateKey.export({
      type: 'pkcs1',
      format: 'pem',
    });
    return [publicKeyString, privateKeyString];
  } catch (e) {
    const err = new Error(e.code || 'keygen error', { cause: e }); err.name = 'KeyGenError';
    throw err
  }
}

function createDirIfNotExists(newPath) {
  if (!fs.existsSync(newPath)) {
    fs.mkdirSync(newPath, { recursive: true });
  }
}

genKeyPair().then((result) => {
  console.log(result)
  createDirIfNotExists('../keys')
  fs.writeFileSync('../keys/public_key.pem', result[0])
  fs.writeFileSync('../keys/private_key.pem', result[1])
}).catch(err => console.log(err))

Only dependency is jose package.json ->

{
  "name": "keygen",
  "version": "1.0.0",
  "description": "Assymetric Keygen Util",
  "main": "app.js",
  "type": "module",
  "scripts": {
    "start": "node app.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "jose": "^4.11.2"
  }
}