basic_javascript.js

//  javascript variable
// let val1 = "consistency is key"   //string 
// console.log(val1,typeof(val1))

// let a = 12 + 34;
// let b = 34 + "b";   //use with concadtion operator 
// let c = 'c' + 7;
// console.log(a,b,c);

// hostingnpm install -g nodemon
// var val 
// console.log(val);
// // undefined 

// let val2var val 
// console.log(val);
// // undefined 

// let val2
// console.log(val2);

// const val3          Missing initializer in const declaration
// console.log(val3)



// function  
// function abc(){
//     console.log("this is title of the abc")
// }
// abc();

//function expression
// let abc = function(){
//     console.log("this is tile of the abc but difference")
// }

// difference between function and function expression : 
// hosting

// object;
const person = {
    firstName: "John",
    lastName: "Doe",
    age: 50,
    eyeColor: "blue"
};

// console.log(person,typeof(person));
// console.log(person["firstName"])
// console.log(person.firstName)


// loops
// for in 
// for of
// foreach 

// to use with iterable in the any variable (which is the object(string,object,array also))
// for(let k in person){
//     // console.log(k);  to print the key 
//     console.log(k,person[k])
// }

// let arr = [34,45,67,89,90]    
// for(let k in arr){
//     console.log(arr[k])
// }

// for of loop 
// iterable object = string, array 
// for (variable of iterable)
//   statement


// let sum = 0;
// for(let element of arr){
//     // console.log(element)
//     sum += element
// }
// console.log(element);


// 
// let arr = [34,45,67,89,90]     

// Array 
let arr = [34,45,67,89,90,56,78,90,23,45]        // array which group of the variable
console.log(arr,typeof(arr))       //which is object 

//Array constructor
//main point about the array that sort m
let arr1 = new Array(7)     //parameter which is length 
// here intialize to array size which creating 7 length but 
// main things that here empty variables add 
console.log(arr1)
// Array(7) [ <7 empty slots> ]

// array method 
// concat method
// const array1 = ['a', 'b', 'c'];
// const array2 = ['d', 'e', 'f'];
// const array3 = array1.concat(array2);
// console.log(array3);

// entries
// const iterator1 = arr.entries();
// // return the iterator
// console.log(iterator1.next().value) //[ 0, 34 ]
// console.log(iterator1.next().value)

// filter
// const eventArr = arr.filter(e => e % 2 == 0);
// const oddArr = arr.filter(e => e % 2 !== 0);
// console.log(eventArr);
// console.log(oddArr);

// find()
const finde = arr.find(e=>e>50)
console.log(finde)  //67

// flatMap()
// return array which is depth one to convert the all subarray to element
// const arr2 = [1, 2, [3], [4, 5], 6, [[[5,6,[90,[5,7,9]]]]]];
// const flatmap = arr2.flatMap(num => num);
// console.log(flatmap);

// Array.from()
// create new array shallow-copied array instance from given existence array
const charArr = Array.from("jayendra");
console.log(charArr)


//main point about the array that sort method sort the string type which lexicographic order
// ex : 
let array = [567,23,12,100,34,20000,3000];
array.sort();
// console.log(array);
// Array(7) [ 100, 12, 20000, 23, 3000, 34, 567 ]

// therefore use to callback in sort method 
array.sort((a,b)=> a-b);
console.log(array);
// Array(7) [ 12, 23, 34, 100, 567, 3000, 20000 ]Person.prototype.calculateAge= function(){
    console.log('The current age is: '+(2019- this.yearOfBirth));

console.log(Person.prototype);

// let x = 9.656;
// x.toFixed(0);
// console.log(x);
// x.toFixed(2);
// console.log(x);
// x.toFixed(4);
// console.log(x);
// x.toFixed(6);
// console.log(x);// function constructor
function Person(name, job, yearOfBirth){   
    this.name= name;
    this.job= job;
    this.yearOfBirth= yearOfBirth;
}
// this will show Person's prototype property.
console.log(Person.prototype);

Array.prototype.calculateAge= function(){
    console.log('The current age is: '+(2019- this.yearOfBirth));
}
console.log(Array.prototype);

const p1 = new Person("jayendra","do",23);
console.log(p1);

const p2 = new Person("nitin","do",45);
console.log(p2);

// function User(firstName, lastName, email, age, address){

//     this.firstName = firstName;
//     this.lastName = lastName;
//     this.email = email;
//     this.age = age;
//     this.address = address;
//     this.about = function(){
//         return `${this.firstName} is ${this.age} years old.`;
//     };
//     this.is18 =  function(){
//         return this.age >= 18;
//     }
// }
// console.log(User.prototype);