These quotes will help you to create your better version.

Don't be worst company of yourself 

Whenever you find yourself wasting time, remember. There is someone out there who is equipping him/her at this very moment. The day you compete with him, you’ll lose.

Your problem is you have spent your whole life thinking there are rules. There aren’t. We used to be gorillas. All we had is what we could take and defend.

If you spend too much time thinking about a thing, you’ll never get it done. ~ Bruce Lee

Life can be hard. But remember, while the difficult moments may decrease happiness, they’re essential for building meaning. And that’s what matters in the long run."

You don't get frustrated because of events. You get frustrated because of your beliefs.

Act the way you’d like to be and soon you’ll be the way you’d like to act.

Anger is not a real emotion. It is fear clothed. Figure out what you are afraid of before you get angry.

God gives his hardest battles to his toughest soldiers." You are being redirected and made strong for a purpose in your life. Its not suffering, its training. Training for you to make it big.

Eat a frog everyday(do your worst task first thing in the morning). It would be actually difficult in the beginning. But as you do it, you will start feeling better and procrastinate less in life.  

And in the end, it’s not the years in your life that count. It’s the life in your years.

Install and use MongoDB in Windows

In this post I will share you how to install and use MongoDB in Windows in easy steps.

Step 1 : Download  MongoDB

Go to  MongoDB's official site and select the suitable version for your system and download.
Here is the link to download : https://www.mongodb.com/download-center?jmp=nav#community

       

Step 2 : Install it

To install  MongoDB go to download location on your computer, double click the file and press Run when pop-up appears.

Step 3 : Add  MongoDB to System Path Variable

Go to control panel then “Edit the system environment variables". when “System Properties” window appears, click on “Environment Variables…” and click on "New.." which appears in the bottom.

 Give Variable name as "Path" and Variable value  as "C:\Program Files\MongoDB\Server\3.4\bin" (navigate to MongoDB's bin folder to get the right path based on your system and folder location). Variable value depends on where you  MongoDB script folder resides.

Step 4 : Run MongoDB server
Open a command prompt window and run the "mongod" command, this command run the "MongoDB" server at "27017" port and ready to connection with a client.

Step 5 : Run MongoDB  client
Open another command prompt window and run the "mongo" command, this command create a client and establish the connection to server running at port "27017".

Step 6 : Create a new database
use studentDetails

Step 7 : Insert Data into database
db.students.insert([{"studentName":"Ankur","marks":"20"},
                                {"studentName":"Raj","marks":"30"}])



Step 7 : Check inserted Data into database
db.students.find().pretty();

I think today you learnt enough about mongoDB, Now go and give a try.

Happy Learning :-)

Javascript interview questions: typeof

Question : what is typeof in javascript
Answer : The typeof operator returns a string indicating the type of the unevaluated operand.
Example : var a = 1;
               console.log(typeof a);// number

Question : Write the output
                console.log(typeof Infinity);
Answer : number

Question : Write the output
                 console.log(typeof null);
 Answer : 'object';

Question : Write the output
                 var a = [1 ,2 ,3];
                 console.log(typeof a);
 Answer : 'object';

Question : Write the output
                 console.log(typeof String('abc'));
 Answer : 'string';

Question : Write the output
                 console.log(new String('abc'));
 Answer : 'object';

Question : Write the output
                 typeof g;
 Answer : "undefined";

Question : Write the output
                 console.log(typeof NaN );
 Answer : "number";
* In ES6 use Number.isNaN() function for checking the value. Otherwise you can also use isNaN() .

Javascript interview questions: Hoisting , delete , use strict

Question Hoisting in Javascript.
Answer: Hoisting is JavaScript's default behavior of moving declarations to the top.

Question: Write the output
              x = 5;
             console.log(x);
             var x;
Answer: 5;

Question: Write the output
           var x;          
           x = 5;
          console.log(x);    
Answer: 5;

Question: Write the output
         "use strict";
         console.log(x);    
         var x;          
         x = 5;
Answer: undefined;

Question: Write the output
         "use strict";
         console.log(x);
          var x = 5;
Answer: undefined;

Question: Write the output
           "use strict";
           console.log(x);
            x = 5;
Answer: Uncaught ReferenceError: x is not define;

Question.  "use strict" in Javascript.
Answer: The purpose of "use strict" is to indicate that the code should be executed in "strict mode".
Syntax : "use strict";

Question: Write the output
       "use strict";
         x = 5;
         console.log(x);
Answer: ReferenceError: x is not defined

Question: Write the output
          x = 5;
          console.log(x);
 Answer: 5
* x will be create as a global varible

Question: Write the output
          "use strict";
          console.log(x);
           x = 5;
Answer: ReferenceError: x is not define;

Question: Write the output
          "use strict";
         var x = y = 2;
Answer: ReferenceError: y is not defined;

Question.  delete in Javascript.
Answer: it will delete object properties.The delete operator will not delete ordinary variables.However, it will delete "global variables," since they are actually properties of the global object.if in strict mode it will throw an error.


Question: Write the output
          "use strict";
           var x = 2;
           delete x;
           console.log(x);
Answer: SyntaxError: Delete of an unqualified identifier in strict mode.

Question: Write the output
            var x = 2;
            delete x;
             console.log(x);
Answer: 2

Question: Write the output
             x = 2;
           delete x;
           console.log(x);
Answer: undefined

Question: Write the output
            var t = "test";
           var test2.t2 = t;
           delete test2.t2;
           console.log(t);
Answer :  "test";

Classes in JavaScript

Classes are the well-known concept in object oriented programming. Programmer those working on C++, Java etc are aware of what is Class and what we can achieve using Classes.With ECMAScript 2015 version JavaScript also introduced Classes.

According to MDN -

"JavaScript classes introduced in ECMAScript 2015 are syntactical sugar over JavaScript's existing prototype-based inheritance. The class syntax is not introducing a new object-oriented inheritance model to JavaScript. JavaScript classes provide a much simpler and clearer syntax to create objects and deal with inheritance."

let's go bit deeper and learn how Classes works in JavaScript.

• JavaScript classes introduced in ECMAScript 2015.
• To declare a class, you use the class keyword with the name of the class.
• JavaScript does not have classes, the way that Java and other languages have classes.
• JavaScript's class is (mostly) just syntactical sugar for prototypes, which are very different from traditional classes.
• A distinctive feature of classes is the function called the constructor. This is where you initialize your object's properties.
• You don't have to define a constructor function. If you choose not to, the engine will insert an empty one for you.
• In JavaScript, there is two way to define the class.

Class declarations: Use the class keyword and give class name.

     class Rectangle{

         constructor(height, width) {

         this.height = height;

         this.width = width;

       }

    }

Class expressions: class expression can be named or unnamed in JavaScript.

     // unnamed

     var Rectangle = class {

     constructor(height, width) {

      this.height = height;

      this.width = width;

    }

  };



      // named

     var Rectangle = class Rectangle {

     constructor(height, width) {

     this.height = height;

     this.width = width;

    }

   };

An important difference between function declarations and class declarations is that function declarations are hoisted and class declarations are not.

    //Example

    var p = new Rectangle(); // ReferenceError

    class Rectangle {}

The constructor method is a special method for creating and initializing an object created with a class. A constructor can use the super keyword to call the constructor of a parent class.

Prototype methods: 

Here is the example to create prototype method in JavaScript

      class Rectangle {

         constructor(height, width) {

         this.height = height;

         this.width = width;

      }

       get area() {
          return this.calcArea();
       }

      calcArea() {
        return this.height * this.width;
     }
   }
    const square = new Rectangle(10, 10);
    console.log(square.area);

Static methods: 

• The static keyword defines a static method for a class.
• Static methods are called without instantiating their class and cannot be called through a class instance. 
• Static methods are often used to create utility functions for an application.Below is the example to create static method in JavaScript.

      class Point {
          constructor(x, y) {
          this.x = x;
          this.y = y;
       }

        static distance(a, b) {
        const dx = a.x - b.x;
        const dy = a.y - b.y;

        return Math.sqrt(dx*dx + dy*dy);
      }
    }

        const p1 = new Point(5, 5);
        const p2 = new Point(10, 10);
        console.log(Point.distance(p1, p2));

ES6 is finalized, but not fully supported by all browsers (e.g., ES6 Firefox support). To use ES6 today, get a compiler like Babel.For more information and examples on ES6 classes, take a look at this link MDN:CLASSES.

Happy Learning :-)

JavaScript ES6 : Difference between var, let and const

   In this tutorial I am going to write about variable declaration in JavaScript.So lets start with some basic difference between var, let and const.

var 

• var is scoped to the nearest function block.
• You can declare the same variable multiple times using var.
• You can use variable before even initialize. 
• Global variables defined with var will be added as properties on the global window object.

    //Example

    function test(){

        for( var i = 0; i < 5; i++ ) {

            //i is visible here
        }

         //i is visible here
     }
     //i is not visible here


   // You can declare the same variable multiple times using var.

    'use strict';
    var a;
    var a;

   //You can use variable before even initialize.

   function fun () {
   typeof a;
   var a = 'big';
   }
   fun();

   /*Global variables defined with var will be added as properties
   on the global window object*/
   

   var  a = 'go';  // globally scoped
   console.log(window.a); // 'go'

let

• let is scoped to the nearest enclosing block (both are global if outside any block), which can be smaller than a function block.
• let says variable will be used only in the block it’s defined in.
• The use case for `let` tends to be for loops or mathematical algorithms.
• Use let where you  need to reassign a variable like in loops.
• Assuming strict mode,you can't declare the same variable multiple times using let.
• Always initialize your identifiers before you try to use them.
• Global variables defined with let will not be added as properties on the global window object

    for( let i = 0; i < 5; i++ ) {
        //i is only visible in here
        //and there is a separate i variable for each iteration of the loop
    }

    //i is not visible here

   // You can't declare the same variable multiple times using let.
   'use strict';
   let a;
   let a; // SyntaxError: Identifier 'b' has already been declared

   //always initialize your identifiers before you try to use them
   function fun () {
   typeof a;
   let a = 'big';
   }  
   fun(); // Uncaught ReferenceError: bar is not defined

   /*Global variables defined with let will not be added as properties
    on the global window object*/
   let a = 'go';  // globally scoped
   console.log(window.a); // undefined

const

• Constants are block-scoped
• The value of a constant cannot change through re-assignment, and it can't be redeclared.
• const says the identifier won’t be reassigned.
• Naming convention for const variable  is to use all-uppercase letters.

   //Example
   // define MY_NUM as a constant and give it the value 17
   const MY_NUM = 17;

   // this will throw an error
   MY_NUM = 20;

   // will print 17
   console.log('my number is: ' + MY_NUM);

   // trying to redeclare a constant throws an error
   const MY_NUM = 20;

   // the name MY_NUM is reserved for constant above, so this will also fail
   var MY_NUM = 20;

   // this throws an error also
   let MY_NUM = 20;

I feel you found this article useful and now you got a clear picture about where and how to  use var, let and const more effectively.

Happy Learning :-)

JavaScript : Data types and operation between data.

     

              JavaScript is the language, which is becoming the universal programming language for the web and currently, it is not only popular for front-end but back-end as well.

When starting with JavaScript people generally get confused with JavaScript data types.In this tutorial, I am going to share how JavaScript data type works.

These are the few key points to mention

• JavaScript is a loosely typed or a dynamic language.
• You don't have to declare the type of a variable ahead of time, it will get determined automatically while the program is being processed.

Data types

The latest ECMAScript standard defines seven data types: 

Six data types that are primitives, primitives are immutable values (values, which are incapable of being changed): 

• Boolean
•  Null
•  Undefined
•  Number
•  String 
• Symbol (new in ECMAScript 6) 

and Object

See the example

Var test  =  "Mark"; // test is a String

Var test  =  123; // test is a Number

Var test  =  true; // test is a Boolean

        Here you can see, I reassigned variable with different type and based on the given value JavaScript will dynamically identify what will the type of the data.Until this stage, everything is perfectly fine but you start getting into the trouble when JavaScript decides the type of the variable based on how that variable is used.

Let see the example:

        '43' - 3  // 40

    3 - '43' //-40

   '4' - '6'//-2

   'er' - 6 // NaN

   6 - 'er' // NaN

   53 + 'y'// "53y"

   'y' + 53 // "y53"

   '4' + '6'// "46"

   '43' + 3 // "433"

   3 + '43' // "343"

   3 + 43 // 46

   '6' * 3 // 18

   '6' * 'b' //NaN

   6 * 'b' //NaN

One way to fix this problem is to be explicit about the variables.check the example

   // previous code

   '43' + 3 // "433"

   // explicit

   var num = "43";

   console.log(parseInt(num, 10) + 3); // 46

In this example, I am using parseInt which is saying to the JS, whatever in the num variable parse that as the integer before performing any operation.This is the one way to get rid of such kind of problem where JavaScript dynamically decides type of data.

Now I feel you understood some basics of the concept, so it's time to give it try.To find more you can check here.
 JavaScript data types and data structures

Happy Learning :-)