function Car(make, model, year) {
this.make = make;
this.model = model;
this.year = year;
}
//create a object with three keys, make, model, and year
var myCar = new Car('Eagle', 'Talon TSi', 1993);
// use the new operator to create any number of car objects with this template object Car above
// New keyword do two things
// 1.) Make an empty object
// 2.) return this
// 3.) assign the function prototype to proto
// Example
function createUser(firstName , age) {
this.firstName = firstName;
this.age = age;
}
createUser.prototype.about = function(){
console.log(`Name of user is ${this.firstName} age of user is ${this.age}`);
}
const user1 = new createUser("Fahad", 23);
// user1.about();
// So if we're defining a function that'll call with new keyword then we make the function and assign capital letter to fast alphabet to tell other developers that it'll call with new keyword otherwise it'll not gonna work...
// EXAMLE
function Hello(firstName) {
this.firstName = firstName;
}
Hello.prototype.hello = function (){
console.log("Hello", this.firstName);
}
const helloTofahad = new Hello("Fahad", 34);
console.log(helloTofahad.hello())
// That's how it'll workObjMaker = function() {this.a = 'first';};
// ObjMaker is just a function, there's nothing special about it that makes
// it a constructor.
ObjMaker.prototype.b = 'second';
// like all functions, ObjMaker has an accessible prototype property that
// we can alter. I just added a property called 'b' to it. Like
// all objects, ObjMaker also has an inaccessible [[prototype]] property
// that we can't do anything with
obj1 = new ObjMaker();
// 3 things just happened.
// A new, empty object was created called obj1. At first obj1 was the same
// as {}. The [[prototype]] property of obj1 was then set to the current
// object value of the ObjMaker.prototype (if ObjMaker.prototype is later
// assigned a new object value, obj1's [[prototype]] will not change, but you
// can alter the properties of ObjMaker.prototype to add to both the
// prototype and [[prototype]]). The ObjMaker function was executed, with
// obj1 in place of this... so obj1.a was set to 'first'.
obj1.a;
// returns 'first'
obj1.b;
// obj1 doesn't have a property called 'b', so JavaScript checks
// its [[prototype]]. Its [[prototype]] is the same as ObjMaker.prototype
// ObjMaker.prototype has a property called 'b' with value 'second'
// returns 'second'It does 5 things:
It creates a new object. The type of this object is simply object.
It sets this new object's internal, inaccessible, [[prototype]] (i.e. __proto__) property to be the constructor function's external, accessible, prototype object (every function object automatically has a prototype property).
It makes the this variable point to the newly created object.
It executes the constructor function, using the newly created object whenever this is mentioned.
It returns the newly created object, unless the constructor function returns a non-null object reference. In this case, that object reference is returned instead.**Important Points**
1.It creates a new object. The type of this object is object.
2.It sets this new object's internal, inaccessible, [[prototype]] (i.e. __proto__) property to be the constructor function's external, accessible, prototype object (every function object automatically has a prototype property).
3.It makes the this variable point to the newly created object.
4.It executes the constructor function, using the newly created object whenever this is mentioned.
5.It returns the newly created object, unless the constructor function returns a non-null object reference. In this case, that object reference is returned instead.
Note: constructor function refers to the function after the new keyword, as in
new ConstructorFunction(arg1, arg2)