javascript interview questions

javascriptInterview.js

(1)  
What are JavaScript Data Types?

Following are the JavaScript Data types:

Number
String
Boolean
Function
Object
Undefined

(2) Given a variable , how do we find which kind of variable it is ? (like Number , String)
Ans : typeof variableName

(3)Explain the difference between "==" and "==="?
  "==" checks only for equality in value whereas "===" is a stricter equality test and returns false 
if either the value or the type of the two variables are different.
(4)What is an undefined value in JavaScript?

Undefined value means the

Variable used in the code doesnot exist
Variable is not assigned to any value
Property doesnot exist

(5)What is the purpose of clearTimeout function?
  
  (6)EventEmitter 
Many objects in a Node emit events, for example, a net.Server emits an event each time a peer connects to it,
  an fs.readStream emits an event when the file is opened. 
All objects which emit events are the instances of events.EventEmitter.

(7)What Are Globals In Node.Js?
Answer.

There are three keywords in Node.js which constitute as Globals. These are Global, Process, and Buffer

(8) Difference between process.nextTick() and setTimeout
he difference between setTimeout() and process.nextTick() is that the process.nextTick() function is specific to the Node.js
Event Loop. setTimeout() uses JavaScript runtime to schedule its own queue of events. 
When using process.nextTick(), callback function associated with it runs immediately after events in the Event Queue are 
processed by the Event Loop in a single iteration. In comparison to setTimeout(), it is faster since queue 
associated with setTimeout()
or the JavaScript runtime.
===========
  const server = net.createServer(() => {}).listen(8080);

server.on('listening', () => {});
When only a port is passed, the port is bound immediately. 
So, the 'listening' callback could be called immediately. The problem is that the .on('listening') 
callback will not have been set by that time.

To get around this, the 'listening' event is queued in a nextTick() to allow the script to run to completion. 
This allows the user to set any event handlers they want.
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