call method in javascript

var person = {

    fullName: function() {

    return this.firstName + " " + this.lastName;

    }
}

var person1 = {

  firstName:"John",

    lastName: "Doe"

  }

var person2 = {

  firstName:"Mary",

    lastName: "Doe"
}

  person.fullName.call(person1);  // Will return "John 
  Doe"
 

var person = {

    fullName: function() {

    return this.firstName + " " + this.lastName;

    }
}

var person1 = {

  firstName:"John",

    lastName: "Doe"

  }

var person2 = {

  firstName:"Mary",

    lastName: "Doe"
}

	person.fullName.call(person1);  // Will return "John 
	Doe"
 

// Define your function
function sayHello(msg){
	console.log("Hello, " + msg);
}

// Call it
sayHello("Norris");

// outputs:
// Hello, Norris

var person = {

  firstName:"John",

  lastName: "Doe",

    fullName: function () {

    return this.firstName + " " + this.lastName;

    }

}

	person.fullName();   // Will return "John Doe"
 

<button onclick="sayHello()">say hello</button>  <script>    'use strict';  //force the context to be undefined    function sayHello() {      console.log(this);      console.log(arguments);      console.log('hello');    }  </script>