variable-scope.js

// Defining Variables:-
 /*let and var is used to declare variables. Const is used to declare a Constant:-- let name="Jack";
             varage="35";
             const earn=1000; */
//---------------------------------------------------
//Naming Convention:--
  /*ALLOWED:-
  -let userName(camelCase)
  -let cric24(only letters & digits)
  -let $special(starting with $)
  -let _internalValue(starting with _allowed) */

  /*NOT ALLOWED:--
  -let user_name(Bad Practice)
  -let 21Players(starting with Numbers)
  -let user-b(special characters not allowed)
  -let let */

//------------------------------------------------
//Variable Declarationn and Variable Initialization
  
/*
var msg;
msg="Hello JavaScript!";// assigned a string value
console.log(msg);// access a variable

//the following declares and assign a numeric value
var num=100;
var hundred=num;// assigned a variable to varible
console.log(hundred);
console.log(num);
*/

/*
let msg;
msg="Hello JavaScript!";// assigned a string value
console.log(msg);// access a variable

//the following declares and assign a numeric value
let num=100;
let hundred=num;// assigned a variable to varible
console.log(hundred);
console.log(num);
*/

/*
 const msg; //Only Declared and not initialized(Error)
 msg="Hello JavaScript!";// assigned a string value(it will not take this value)
 console.log(msg);// Cannot access a variable

//the following declares and assign a numeric value
const num=100;
const hundred=num;// assigned a variable to varible
console.log(hundred);
console.log(num);
*/

//---------------------------------------
//ARITHEMATIC OPERATORS

//1. + [Add Two Numbers](right to left)
 let a=5, b=5;
 console.log(a + b);


//2. - [Subtract two Numbers](right to left)
 let a=5, b=5;
 console.log(a - b);

//3. * [Multiply two numbers](left to right)
 let a=5, b=5;
  console.log(a * b);


//4. / [divide two numbers](left to right)
 let a=5, b=5;
 console.log(a / b);


//5. % [divide two numbers and gives remainder](left to right)
 let a=5, b=5;
  console.log(a % b);


//6. ** [exponentiation] (2 ** 3 =8)
 let a=5, b=5;
  console.log(a ** b);


//7. = [Assign Value]


//8. += [perform addition and re-Assign Value]
 let a=5, b=6; 
 console.log(a += b);


//9. -= [Perform Substraction and re-Assign value]
 let a=5, b=5;
 console.log(a -= b);


//10 ++ [Increment and re-assign]
//POST-INCREMENT
let a=5;
console.log(a++); //5, Because it will increment the value by One but Evaluates/Assign the Value Before Increment

//PRE-INCREMENT
let b=5;
console.log(++b); //6, Because it will increment the value by one and Evaluates/Assign the NEW VAlUE.


//11. -- [Decrement And re-Assign]
 let a =5;
 console.log(a--); //5, Because it will decrement the value by One but Evaluates/Assign the Value Before decrement
 console.log(a--); //4

 let a =5;
 console.log(--a); //4, Because it will decrement the value by One and Evaluates/Assign the Value after decrement
 console.log(--a); //3

//--------------------------------------------------
 //Number and String
  let saving = 300;

  console.log(`Hello CK. You have net worth of $${saving}`);
  console.log('Hello CK. You have net worth of $'+saving+'')
  console.log("Hello CK. You have net worth of $"+saving+"")

//ESCAPE Characters
// --\n = new Line
// --\t = Horizontal Tabulator
// --\' = Single Quote
// --\" = Double Quote

//------------------------------------------------
//ARRAY
 let arr= [1,2,3,4,5];
 let age=30;
 let arr1= ["ck",2,arr, ["a","b"],age];
 console.log(arr1[0]);
 console.log(arr1[3][0]);
 console.log(arr1[2][4]);

//------------------------------------------------------------
 //OBJECTS
  let obj= {name:"CK",
  age:30,
  nationality:"Indian",};

  console.log(obj);
  console.log(obj.name);
  console.log(obj["nationality"]);

//----------------------------------------------------------
/*
let name='2';
console.log(parseInt(name)+2); //4, Adds the Numbers-- parseInt converts string into Numbers
console.log(name+2); //22, it takes '2' as a string
*/

//-------------------------------------------------------
 //Function
//   function add(a, b) {
//   let result = a + b;
//   console.log(result)
//  }

//  add(3, 4);

//-------------------------------------------------------------
//  function add(a, b) {
//   const results = a + b;
//   return results;  
//  }


//--------------------------------------------------------
 //typeof Operator

 function getMessage() {
   console.log("this is test message");
   return 5;
 }

 let arr= [1,2,3,4];
 let obj= {name:"CK",
 age:30,
 nationality:"Indian",};

 let age= 30;
 let myName="CK";

 console.log("Type of UNDEFINED :"+ typeofundefined); //it will not work, it is not in BRACKET.. 
 console.log("Type of NULL :"+ typeof(null));
 console.log("Type of NaN :"+ typeof(NaN));
 console.log("Type of Function :"+ typeof(getName));
 console.log("Type of Array :"+ typeof(arr));
 console.log("Type of Object :"+ typeof(obj));
 console.log("Type of Number :"+ typeof(age));
 console.log("Type of String :"+ typeof(name));
 console.log("Type of Boolean :"+ typeof(myName=="CK"));
 console.log(typeof(nationality));
 console.log("Type of Function: " + typeof(Function));

 arr =[12,44,55,3,552,]
 console.log(arr[1]);
 console.log(typeof(arr));

 console.log(typeof(Null));       //object
 console.log(typeof(arr));          //object
 console.log(typeof ("John"))              // Returns "string"
 console.log(typeof (3.14))                // Returns "number"
 console.log(typeof (NaN))                 // Returns "number"
 console.log(typeof (falsse))                  // Returns "boolean"
 console.log(typeof ([1,2,3,4]))              // Returns "object"
 console.log(typeof ({name:'John', age:34}))  // Returns "object"
 console.log(typeof (new Date()))             // Returns "object"
 console.log(typeof (function () {}))         // Returns "function"
 console.log(typeof (myCar))                  // Returns "undefined" *
 console.log(typeof (null))                   // Returns "object"
 console.log(typeof(undefined));

//--------------------------------------------------------------
 //UNDEFINED:- Default value of uninitialized variables

 //NULL:- never assumed by default 

 //NaN:- result of invalid calculations


//------------------------------------------------------
 //Array
  const arr1= [1,2,3];
  console.log(arr1);
 
  const arr = new Array(5);
  console.log(arr) //5 Empty items


  const arr1 = Array(5);
  console.log(arr1); //5 empty items

  const arr2 = Array.of(1, 2); 
  console.log(yetMoreNumbers); //error
  console.log(arr2); //[1, 2]

/CONVERT STRING INTO ARRAY 
const arr3 = Array.from("hello");
 console.log(arr3); //Split [h, e, l, l, o]
 

//----------------------------------------------------------
//  //Array Operations(push, pop, shift, unshift)
  const hobbies= ["Sports","Cooking"];
  console.log(hobbies.push("Reading")); // add element at the end of the array
  console.log(hobbies);
  console.log(hobbies.unshift("Coding")); // add at the begining of the array
  console.log(hobbies);
  const poppedValue=hobbies.pop(); // Remove from the end of the array
  console.log(poppedValue); //and returns the remvoed element
  let removedEle = hobbies.shift(); // Remove fromthe beginning of the arrray
  console.log(removedEle);
  console.log(hobbies);

 
 //----------------------------------------------------------
  //SLICE    
  const arr = [23, 553, 46, 677, 57];
  console.log(arr.slice(1, 3));

//-------------------------------------------------------------
 //SPLICE() METHOD

  const hobbies= ["Sports","Cooking"];
  console.log(hobbies.splice(0,0,1,"one"));
  console.log(hobbies);
  let val=hobbies.splice(0,0,"singing");
  console.log(val);
  console.log(hobbies);
  const removedElements=hobbies.splice(-2,2,"running");
  console.log(hobbies);
  console.log(removedElements);
  console.log(hobbies);


 //-----------------------------------------------------
  //ARRAY CONCAT
  const arr1 =[12, 33, 44, 555];

  let newArr = arr1.concat([23424, 23525, 235542]);
  console.log(newArr.push(34));
  console.log(newArr);


//------------------------------------------------------------
 //Indexof and Lastindex

  const testResults= [1, 5.3, 1.5, 10.99, -5, 1.5, 10];
  console.log(testResults.indexOf(1.5));
  console.log(testResults.indexOf(1.5,3));
  console.log(testResults.lastIndexOf(1.5));
  console.log(testResults.lastIndexOf(1.5, -1));
  console.log(testResults.lastIndexOf(22));
  const personData= [{name:"CK"}, {name:"Prabhat"}];
  console.log(personData.indexOf({name:"CK"}));
  console.log(personData.lastIndexOf({name:"prabhat"}));


//----------------------------------------------------------------
/* Q2. write a program to print the below pattern of stars.
*
**
***
****
***** */

//A2:-

/*
for (var i=1; i<=5; i++){
  console.log("*".repeat(i));
}

//--------------------------------------------------------------------------------
/* Q3. write a program to print the pyramid of stars. */ 

//A3.

function pyramid(n){
  for(let i=1; i<=n; i++){
    let str =" ".repeat(n-i);
    let str2 ="*".repeat(i*2 -1)

    console.log(str + str2 + str);
  }
}
pyramid(5);
      
//----------------------------------------
 //REVERSE PYRAMID
      
let n = 5;
// External loop
for (let i = 0; i < n; i++) {
  // printing spaces
  for (let j = 0; j < i; j++) {
    process.stdout.write(' ')
  }
  // printing star
  for (let k = 0; k < 2 * (n-i) - 1; k++) {
    process.stdout.write('*')
  }
  console.log();
}

//-------------------------------------------------------------
//when we have array of objects we use the find() and findIndexOf() to take out the element NOT INDEX.. 
//Find() 
 //findIndex()
 
    const personData = [{name:"VK"}, {name:"NN"}];
    console.log(personData.indexOf({name:"VK"}));

    const myName = personData.find((person, idx, persons) => {
     console.log(idx, "idx");
     return person.name === "VK"
    });
    console.log(myName, personData)

    const myIndex =personData.findIndex((person, idx, persons) => {
     console.log(idx, "index");
     return person.name === "NN"
    })
    console.log(myIndex);


//-----------------------------------------------------------
 //ARRAY REVERSE
//BEST SHORT METHOD
  var arr = [1, 2, 3, 4, 5, 6, 7];
 console.log (arr.reverse());

//------------------------------------------------------------
 //ARRAY SORT[BUBBLE SORT]
 
let numbers = [0, 123 , 223, 53, 130, 20, 30 ];
numbers.sort( function( a , b){
    if(a > b) return 1; //always use positive value for ascending sort here, use negative value to sort descending

    if(a < b) return -1; //always use negative value for ascending here, use positive value to sort desscending
    return 0;
});

console.log(numbers)

//---------------------------------------------------------
 //SORT-REVERSE together
  
const prices= [5.99,10.99,3.99,6.59];
const names= ["ck","Prabhat","Yogesh","Haresh"];
const info= [{name:"CK"}, {name:"Prabhat"}, {name:"Haresh"}];
let sortedValue=prices.sort((a,b) => {if(a>b) {
  return 1; //always use positive value here, use negative value to sort reverse
} else if(a===b) {
  return0;
} else {
  return -1; //always use negative value here, use positive value to sort reverse
}});
console.log(prices);
console.log(sortedValue);
console.log(sortedValue.reverse());



//--------------------------------------------------
 //Filter()
  const prices = [22, 555, 56, 567]
  let filterValue = prices.filter((price, idx, prices) => {
   return price > 500;
  });
  console.log(prices);
  console.log(filterValue);


//---------------------------------------------------------
 //Includes()
  const test = [12,3313,441,4141,41414,1241455,]

  console.log(test.indexOf(441,1));
  console.log(test.includes(12));
  console.log(test.includes(54545));
  console.log(testResults.indexOf(11) !== -1); //FALSE

//--------------------------------------------------------------
//forof-- for Array and forin--- for Objects 
//forEach() is like forof
  const arr =[2.22, 13, 665,-433, 677.3]
  for(let value of arr)
  console.log(value);
 
  for(let o in arr) {
  console.log(o)
  console.log(arr[o])
  }

//forEach
 const articlePrice = [2133, 13331 ,1233, 3646, 57678];

 const shipping = 1500;

 const totalPrices = [];

  for(let value of articlePrice) {
   totalPrices.push(value + shipping);
  }
  console.log(value);
  console.log(totalPrices);

articlePrice.forEach((value, idx, articlePrice) => {
  const artvalue = { index: idx, totalPrice: value + shipping}
  totalPrices.push(artvalue);
});
console.log(totalPrices);

//--------------------------------------------------------
 //MAP
 const articlePrices= [10.99,5.99,3.99,6.59];

 const tax=1.2;

 const totalPrices=articlePrices.map((value, idx, articlePrices) => {
  const artvalue= {index:idx, totalPrice: value + tax };
  return artvalue;
});
console.log(totalPrices);

//--------------------------------------------------------
 //ARRAY DESTRUCTING
 const userDetails= ["Max","Schwarz","Mr",30];
//  const firstName = userName[0];
 // const lastName = nameData[1];
 const[firstName,lastName, ...otherInformation]=nameData;
 console.log(firstName);
 console.log(lastName);
 console.log(otherInformation);


//----------------------------------------------------
 //ARRAY Reduce
 const prices= [10.99,5.99,3.99,6.59];
 const sum=prices.reduce((total, curValue, currentIndex, arr) => {
  return total + curValue;
},0);
console.log(prices);
console.log(sum);

//-------------------------------------------------------
 //SPLIT() //CONVERT STRING TO ARRAY
 const text = "Welcome to JavaScript Tutorial - ItsJavaScript";

// split the text into words using space as delimiter
 const substr = text.split(" ");
 console.log(substr);

 //split the text into SINGLE LETTERS
 const sub = text.split("");
 console.log(sub);

//------------------------------------------------------------
 //JOIN() //CONVERT ARRAY TO STRING

const name = ["V", "C"];
let joinedname = name.join("");
console.log(joinedname)


 const myText = "It is a long established fact that a reader will"
 const newText = myText.split(" ").join("")
 console.log(newText);


//----------------------------------------------------
 //SPREAD OPERATOR
//  const numbers = [11,231,14,4155,];
//  const altNumbers = [...numbers];
// //  console.log(altNumbers);
//  console.log(altNumbers.push(6767, 98));
// //  console.log(numbers);
// console.log(altNumbers);

//
const prices= [10.99,5.99,3.99,6.59];
const copiedPrices= [...prices];
prices.push(12.99);
console.log(prices,copiedPrices["0"]);



//------------------------------------------------------
 //REVERSE with For Loop
//  var arr = [1, 2, 3, 4];
//  for (let i = 0; i < Math.floor(arr.length / 2); i++) {
//     [arr[i], arr[arr.length - 1 - i]] = [arr[arr.length - 1 - i], arr[i]]; 
//  }
//  console.log(arr);

//------------------------------------------------------------
 //Reverse with function reverse
 function reverse(array) {
   var output = [];
   while (array.length) {
     output.push(array.pop());
   }

   return output;
 }

 console.log(reverse([1, 2, 3, 4, 5, 6, 7]));

//----------------------------------------------------------
 //*Reverse a STRINg with Function with "" i.e COMMA
 let string = "vinay"; 
 console.log(string.split("").reverse().join(""));
 
 //*Reverse a String with Function witout ""
 let str = "vinay"; 
 console.log(str.split("").reverse().join());


//------------------------------------------------------------
 //Reverse String
 // program to reverse a string
  function reverseString(str) {

//   // empty string
   let newString = "";
   for (let i = str.length - 1; i >= 0; i--) {
       newString += str[i];
   }
   return newString;
 }
 // take input from the user
 const string = ('Hello World');

 const result = reverseString(string);
 console.log(result);


//-----------------------------------------------------
 //Reverse String with Function
  // program to reverse a string

function reverseString(str) {

  // return a new array of strings
  const arrayStrings = str.split("");
 
  // reverse the new created array elements
  const reverseArray = arrayStrings.reverse();

  // join all elements of the array into a string
  const joinArray = reverseArray.join("");
  
  // return the reversed string
  return joinArray;
}

// take input from the user
const string = ('Hello');

const result = reverseString(string);
console.log(result);

 


//-------------------------------------------------
 //IF-ELSE IF -ELSE
let age = 158;
if(age < 18) {
  console.log("not adult");
} else if (age > 48) {
  console.log("you are old");
} else {
  console.log("you are adult")
};


//-------------------------------------------------------------------------------
//Logical Operators
             /*
               *AND(&&)
               *OR(||)
               *NOT(!)
              */
//AND OPERATOR(&&)
 -used for boolean operations on two values.
 -returs true if and only if its first and second Operand are true.
   
   let x =10, y =10;
    if (x===10&&y===10){
     console.log("true");
     }else {
     console.log("false");
      
//OR (||)
      performs boolean expressions on two relational values.
       -returs true if one or both operands are true.*/

let x=10, y=10;
 if (x===10||y===10) {
  console.log("true");
 } else {
  console.log("false")
 };

      
 //NOT (!)
      -Unary operator
      -it is placed before the single operand.*/
 if X =True;
  use ! i.e
 !x =False


      
      
//---------------------------------------------------------
 //EQUALITY
 let obj1 = {name:"CK"};
 let obj2 = {name:"CK"};
 console.log(obj1==obj2);
 console.log(obj1===obj2);

 let obj3 = obj2;
 console.log(obj2===obj3);
 console.log(obj2==obj3);

 let arr1 = ["sports","cooking"];
 let arr2 = ["sports","cooking1"];
 let arr3 = arr2;
 console.log(arr1==arr2);
 console.log(arr1===arr2);
 console.log(arr2===arr3);
      
     
//--------------------------------------------------
 //TERNARY OPERATOR
  2 > 3 ?   console.log("true value") : console.log("false");