this keyword in javascript

var a = 5;

function hi() {
  let a = 10;
  console.log(a);    //scope is the parent function
  console.log(this.a);    //scope is the scope of the parent function i.e window object
}
hi();

// output 
// ----------
// 10
// 5

//Checking the same code with arrow function

var a = 50;
const hi = () => {
  let a = 100;
  console.log(a); //scope is the parent function
  console.log(this.a); //scope is the scope of the parent function i.e window object
};
hi();

// output 
// ----------
// 10
// 5

var a = 5;
function hello() {
  var a = 10;
  function hi() {
    console.log(a);
    console.log(this.a);
  }
  hi();
}

hello();

// this will always point global scope

var name = "shekhar";
const obj1 = {
  name: "Himanshu",
  age: 24,
  getMe() {
    console.log("get me", this.name);
  },
};
obj1.getMe();

//output - 
//get me Himanshu

var name = "john";

const obj1 = {
  name: "rock",
  age: 24,
  getDetails() {
    var name = "rey";
    console.log("One", this.name);
  },
  func1: {
    name: "edge",
    getMe() {
      console.log("Two", this.name);
    },
  },
};
obj1.getDetails();
obj1.func1.getMe();

//output
//john
//get me edge

var name = "himanshu";

var demo2 = () => {
  var name = "shekhar";
  var demo3 = () => {
    console.log(this.name); 
  };
  demo3();
};
demo2();

var a = 10;
console.log(this.a)

const user = {
  firstName: "Him",
  getName() {
    const firstName = "Shekh";
   return this.firstName
  },
};
console.log(user.getName());

//Him

function makeUser() {
  return {
    name: "Himanshu",
    ref() {
      return this;
    },
  };
}

let user = makeUser();
console.log(user.ref().name);

const object = {
  message: "Hello, World!",
  logMessage() {
    console.log(this.message); // What is logged?
  },
};
setTimeout(object.logMessage, 1000);

const object = {
  who: 'World',
  greet() {
    return `Hello, ${this.who}!`;
  },
  farewell: () => {
    return `Goodbye, ${this.who}!`;
  }
};

console.log(object.greet());    // What is logged?
console.log(object.farewell()); // What is logged?

var name = "himanshu";
var street = 50;
var city = "kolkata";

var obj = {
  name: "shekhar",
  street: 46,
  city : "agra",
  sum1: function () {     
    console.log("normal fun", this.street); 
  },
  sum2: () => {    
    console.log("arrow fun" , this.street); 
  },
  address : {
  		houseName : "pathak lane",
      landmark : "icici bank",
      city : "ranchi",
      place : function() {
      			console.log(this.city)
      }
  }
};
obj.sum1()
obj.sum2();
obj.address.place();

const bfObject = {
  value: 42,
  gfFunction: function() {
    setTimeout(function() {
      console.log("Result: ", this.value);
    }, 1000);
  },
}

bfObject.gfFunction();

const obj1 = {
  name: "him",
  roll: "19",
};

const obj2 = {
  name: "him",
  roll: "19",
};

const obj = { 
    name : "Jhon" , 
    sayHi : function(){
        const greet = function(){
            console.log("hello "+ this.name)
        }
        greet();
    }
}

obj.sayHi();

//Input:
const users = [
   ["David", "USA", 30],
   ["Billy"', "Japan", 35),
   ["Mike", "Singapore", 50]
];

//Output:
/* 

[{
"name": "David"
"country": "USA",
"age": 30
},
{
"name": "Billy"
"country":"Japan"
"age": 35
},
{
"name": "Mike"
"country": "Singapore"
"age": 50
}
] 

*/

const obj = {
  value: 42,
  regularMethod: function () {
    setTimeout(function () {
      console.log(this);
    }, 3000);
  },
};

obj.regularMethod();

const {firstName, lastName} = {firstName:"john", lastName:"kennedy"};
console.log(firstName);  // john

let person = {
name: 'John',
age: 30,
greet: function() {
console.log(`Hello, my name is ${this.name} and I am ${this.age} years old`);
}
};

let employee = Object.create(person);
employee.jobTitle = 'Software Developer';

let person = {
name: 'John',
age: 30,
greet: function() {
console.log('Hello, my name is ' + this.name + ' and I am ' + this.age + ' years old.');
}
};

person.greet(); 

let name = "hs";

let user = {
  name: "what about coding",
  deep : {
      wac1: () => {
        console.log("arrow func " + this.name); // no 'this' binding here
      },  
  },
  
  wac2() {
    console.log("normal func " + this.name); // 'this' binding works here
  },
};

user.deep.wac1();
user.wac2();