JavaScript creation Object (ii)

Prototype mode: Each create a function has a prototype attribute, it is a pointer to an object;

How the prototype mode creates the function:

function Movie () {

};
Movie.prototype.name= "Interstellar";
movie.prototype.year=2014;
Movie.prototype.country= "American";
Movie.prototype.playmovie=function () {
alert (this.name);
}

var movie1=new Movie ();
Movie1.playmovie ();//interstellar;
var movie2=new Movie ();
Movie2.playmovie ();//interstellar;

alert (movie1.playmovie==movie2.playmovie);//true distinct from constructors

Object literal amount of way

function Movie () {

};
movie.prototype={
Name: "Interstellar",
year:2014,
Country: "American",
Playmovie:function () {
alert (this.name);
}
}
This way the Contructor property of the prototype object does not point to the movie, but to object.

Whenever the code reads a property, it searches for the object instance itself, does not continue to search for the prototype object that the pointer points to, and ends if it does; the hasOwnProperty () allows you to detect whether the property exists in the instance or in the prototype:

function Movie () {
};
Movie.prototype.name= "Fleetoftime";
movie.prototype.year=2014;
"Movie.prototype.country=";
Movie.prototype.playmovie=function () {
alert (this.name);
}
var movie1=new Movie ();
Alert (Movie1.hasownproperty ("name"));//False on the prototype
Movie1.name= "XXXX";
Alert (Movie1.hasownproperty ("name"));//overwrite the prototype and become true on the instance

The dynamics of a prototype: any modifications made to the prototype object can be immediately reflected from the example:

var movie=new movie ();
Movie.prototype.playone=function () {
Alert ("one");
};
Movie.playone ()//"one"

Adds a method to the movie prototype object

But if you rewrite the entire prototype object, then you cut off the connection between the constructor and the original prototype:

function Movie () {

}

var movie=new moive ();
overriding a prototype object
movie.prototype={
constructor:movie,//object literal to force point to Movie, which would point to object
Name: "XXX",
year:2012,
Country: "XXXX",
Sayname:function () {}
}
The call to the Sayname () method will make an error
Movie.sayname ();//error

Problem with a prototype object: There is a big problem with attributes that contain reference type values, as shown in the following example

function Movie () {
}
movie.prototype={
Constructor:movie,
Name: "XXX",
year:2014,
"place:[", "Japan"],
Playname:function () {
alert (this.name);
}
}
var movie1=new Movie ();
var movie2=new Movie ();

Movie1.place.push ("Korea");

Alert (Movie1.place)//"China,japan,korea"

Alert (Movie2.place)//"China,japan,korea"

It was originally intended to change the place of movie1, and the result was changed to Movie2

The best way to create objects: Constructors to define instance properties, prototype patterns to define methods and shared properties;

function Movie (name,year,country) {
This.name=name;
This.year=year;
This.country=country
"this.place=[", "Japan"];
}
movie.prototype={
Constructor:movie,
Playname:function () {
alert (this.name);
}
}

var movie1=new Movie ("Interstellar", 2014, "American");
var movie2=new Movie ("Fleetoftime", 2014, "a");
Movie1.place.push ("Korea");
alert (movie1.place);//"China,japan,korea"
alert (movie2.place);//"China,japan"

alert (movie1.place==movie2.place);//false
alert (movie1.playname==movie2.playname);//true