ما شی را در 🧑🏻‍💻جاوا اسکریپت⤵️ می شناسیم

//scope.js
a = "JavaScript"; // declaring a variable without let or const make it available in window object and this found anywhere
b = 10; // this is a global scope variable and found in the window object
function letsLearnScope() {
  console.log(a, b);
  if (true) {
    console.log(a, b);
  }
}
console.log(a, b); // accessible

//scope.js
let a = "JavaScript"; // is a global scope it will be found anywhere in this file
let b = 10; // is a global scope it will be found anywhere in this file
function letsLearnScope() {
  console.log(a, b); // JavaScript 10, accessible
  if (true) {
    let a = "Python";
    let b = 100;
    console.log(a, b); // Python 100
  }
  console.log(a, b);
}
letsLearnScope();
console.log(a, b); // JavaScript 10, accessible

//scope.js
let a = "JavaScript"; // is a global scope it will be found anywhere in this file
let b = 10; // is a global scope it will be found anywhere in this file
// Function scope
function letsLearnScope() {
  console.log(a, b); // JavaScript 10, accessible
  let value = false;
  // block scope
  if (true) {
    // we can access from the function and outside the function but
    // variables declared inside the if will not be accessed outside the if block
    let a = "Python";
    let b = 20;
    let c = 30;
    let d = 40;
    value = !value;
    console.log(a, b, c, value); // Python 20 30 true
  }
  // we can not access c because c's scope is only the if block
  console.log(a, b, value); // JavaScript 10 true
}
letsLearnScope();
console.log(a, b); // JavaScript 10, accessible

//scope.js
function letsLearnScope() {
  var gravity = 9.81;
  console.log(gravity);
}
// console.log(gravity), Uncaught ReferenceError: gravity is not defined

if (true) {
  var gravity = 9.81;
  console.log(gravity); // 9.81
}
console.log(gravity); // 9.81

for (var i = 0; i < 3; i++) {
  console.log(i); // 0, 1, 2
}
console.log(i); // 3

//scope.js
function letsLearnScope() {
  // you can use let or const, but gravity is constant I prefer to use const
  const gravity = 9.81;
  console.log(gravity);
}
// console.log(gravity), Uncaught ReferenceError: gravity is not defined

if (true) {
  const gravity = 9.81;
  console.log(gravity); // 9.81
}
// console.log(gravity), Uncaught ReferenceError: gravity is not defined

for (let i = 0; i < 3; i++) {
  console.log(i); // 0, 1, 2
}
// console.log(i), Uncaught ReferenceError: i is not defined

const person = {};

const rectangle = {
  length: 20,
  width: 20,
};
console.log(rectangle); // {length: 20, width: 20}

const person = {
  firstName: "MD",
  lastName: "Shaikh",
  age: 250,
  country: "INDIA",
  city: "Mum",
  skills: [
    "HTML",
    "CSS",
    "JavaScript",
    "React",
    "Node",
    "MongoDB",
    "Python",
    "D3.js",
  ],
  isMarried: false,
};
console.log(person);

const person = {
  firstName: "MD",
  lastName: "Shaikh",
  age: 250,
  country: "INDIA",
  city: "Mum",
  skills: [
    "HTML",
    "CSS",
    "JavaScript",
    "React",
    "Node",
    "MongoDB",
    "Python",
    "D3.js",
  ],
  getFullName: function () {
    return `${this.firstName}${this.lastName}`;
  },
  "phone number": "+3584545454545",
};

// accessing values using .
console.log(person.firstName);
console.log(person.lastName);
console.log(person.age);
console.log(person.location); // undefined

// value can be accessed using square bracket and key name
console.log(person["firstName"]);
console.log(person["lastName"]);
console.log(person["age"]);
console.log(person["age"]);
console.log(person["location"]); // undefined

// for instance to access the phone number we only use the square bracket method
console.log(person["phone number"]);

const person = {
  firstName: "MD",
  lastName: "Shaikh",
  age: 250,
  country: "INDIA",
  city: "Mum",
  skills: [
    "HTML",
    "CSS",
    "JavaScript",
    "React",
    "Node",
    "MongoDB",
    "Python",
    "D3.js",
  ],
  getFullName: function () {
    return `${this.firstName} ${this.lastName}`;
  },
};

console.log(person.getFullName());
// MD Shaikh

const person = {
  firstName: "MD",
  lastName: "Shaikh",
  age: 250,
  country: "INDIA",
  city: "Mum",
  skills: [
    "HTML",
    "CSS",
    "JavaScript",
    "React",
    "Node",
    "MongoDB",
    "Python",
    "D3.js",
  ],
  getFullName: function () {
    return `${this.firstName} ${this.lastName}`;
  },
};
person.nationality = "Ethiopian";
person.country = "INDIA";
person.title = "teacher";
person.skills.push("Meteor");
person.skills.push("SasS");
person.isMarried = true;

person.getPersonInfo = function () {
  let skillsWithoutLastSkill = this.skills
    .splice(0, this.skills.length - 1)
    .join(", ");
  let lastSkill = this.skills.splice(this.skills.length - 1)[0];

  let skills = `${skillsWithoutLastSkill}, and ${lastSkill}`;
  let fullName = this.getFullName();
  let statement = `${fullName} is a ${this.title}.\nHe lives in ${this.country}.\nHe teaches ${skills}.`;
  return statement;
};
console.log(person);
console.log(person.getPersonInfo());

MD Shaikh is Learning Js.
He lives in INDIA.
He Knows HTML, CSS, JavaScript, React, Node, MongoDB, Python, D3.js, Meteor, and SasS.

const person = {
  firstName: "MD",
  age: 250,
  country: "INDIA",
  city: "Mum",
  skills: ["HTML", "CSS", "JS"],
  title: "teacher",
  address: {
    street: "Heitamienkatu 16",
    pobox: 2002,
    city: "Mum",
  },
  getPersonInfo: function () {
    return `I am ${this.firstName} and I live in ${this.city}, ${this.country}. I am ${this.age}.`;
  },
};

//Object methods: Object.assign, Object.keys, Object.values, Object.entries
//hasOwnProperty

const copyPerson = Object.assign({}, person);
console.log(copyPerson);

const keys = Object.keys(copyPerson);
console.log(keys); //['firstName', 'age', 'country','city', 'skills','title', 'address', 'getPersonInfo']
const address = Object.keys(copyPerson.address);
console.log(address); //['street', 'pobox', 'city']

const values = Object.values(copyPerson);
console.log(values);

const entries = Object.entries(copyPerson);
console.log(entries);

console.log(copyPerson.hasOwnProperty("name"));
console.log(copyPerson.hasOwnProperty("score"));

   const users = {
     Alex: {
       email: 'alex@alex.com',
       skills: ['HTML', 'CSS', 'JavaScript'],
       age: 20,
       isLoggedIn: false,
       points: 30
     },
     Asab: {
       email: 'asab@asab.com',
       skills: ['HTML', 'CSS', 'JavaScript', 'Redux', 'MongoDB', 'Express', 'React', 'Node'],
       age: 25,
       isLoggedIn: false,
       points: 50
     },
     Brook: {
       email: 'daniel@daniel.com',
       skills: ['HTML', 'CSS', 'JavaScript', 'React', 'Redux'],
       age: 30,
       isLoggedIn: true,
       points: 50
     },
     Daniel: {
       email: 'daniel@alex.com',
       skills: ['HTML', 'CSS', 'JavaScript', 'Python'],
       age: 20,
       isLoggedIn: false,
       points: 40
     },
     John: {
       email: 'john@john.com',
       skills: ['HTML', 'CSS', 'JavaScript', 'React', 'Redux', 'Node.js'],
       age: 20,
       isLoggedIn: true,
       points: 50
     },
     Thomas: {
       email: 'thomas@thomas.com',
       skills: ['HTML', 'CSS', 'JavaScript', 'React'],
       age: 20,
       isLoggedIn: false,
       points: 40
     },
     Paul: {
       email: 'paul@paul.com',
       skills: ['HTML', 'CSS', 'JavaScript', 'MongoDB', 'Express', 'React', 'Node'],
       age: 20,
       isLoggedIn: false,
       points: 40
     }
   }```

js
const users = [
  {
    _id: "ab12ex",
    username: "Alex",
    email: "alex@alex.com",
    password: "123123",
    createdAt: "08/01/2020 9:00 AM",
    isLoggedIn: false,
  },
  {
    _id: "fg12cy",
    username: "Asab",
    email: "asab@asab.com",
    password: "123456",
    createdAt: "08/01/2020 9:30 AM",
    isLoggedIn: true,
  },
  {
    _id: "zwf8md",
    username: "Brook",
    email: "brook@brook.com",
    password: "123111",
    createdAt: "08/01/2020 9:45 AM",
    isLoggedIn: true,
  },
  {
    _id: "eefamr",
    username: "Martha",
    email: "martha@martha.com",
    password: "123222",
    createdAt: "08/01/2020 9:50 AM",
    isLoggedIn: false,
  },
  {
    _id: "ghderc",
    username: "Thomas",
    email: "thomas@thomas.com",
    password: "123333",
    createdAt: "08/01/2020 10:00 AM",
    isLoggedIn: false,
  },
];

const products = [
  {
    _id: "eedfcf",
    name: "mobile phone",
    description: "Huawei Honor",
    price: 200,
    ratings: [
      { userId: "fg12cy", rate: 5 },
      { userId: "zwf8md", rate: 4.5 },
    ],
    likes: [],
  },
  {
    _id: "aegfal",
    name: "Laptop",
    description: "MacPro: System Darwin",
    price: 2500,
    ratings: [],
    likes: ["fg12cy"],
  },
  {
    _id: "hedfcg",
    name: "TV",
    description: "Smart TV:Procaster",
    price: 400,
    ratings: [{ userId: "fg12cy", rate: 5 }],
    likes: ["fg12cy"],
  },
];