JavaScript Best Practices

The latest ECMAScript standard defines 7 data types:

• Six data types that are primitives:
  • Boolean
  • Null
  • Undefined
  • Number
  • String
  • Symbol (new in ECMAScript 6)
• and Object

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures

best way to check something is available
if(typeof x !== 'undefined'){
    console.log('Exists');
}else{
    console.log('Not Exists');
}

Equality
==   If variables are 2 diffrent types , it will convet them to the same type and check
=== There will be no type conversion

Use === as default.

Node.js ENV variable
Use  node-foremon or nodemon