Four ways to create objects in JS

There are 4 ways to create objects:

• 1. Create objects using literal values
• 2. Use the new character to create an object
• 3. Custom constructor
• 4. Factory pattern creates objects

An object has properties and methods.

1. Create objects by literal value

var person1 = {

    name:'Conan',

    age:12,

    sex:'male',

    eat:function(){

        console.log("I'm hungry and want to eat")

    },

    say:function(){

        console.log("My name is Conan")

    }

}

console.log("person.eat output function",person.eat)

person.eat(); //Directly output I am hungry and want to eat

What we need to pay attention to is: the difference between person.eat and person.eat()

• person.eat is the output function
• person.eat() is the calling function

2. Use the new character to create an object

var person2 = new Object();

person2.name = 'Conan'

person2.age = '21'

person2.sex = 'male'

person2.eat=function(){

    console.log("I'm hungry and want to eat")

}

person2.say=function(){

    console.log("My name is Conan")

}

console.log('sex',person2.sex) //output male

The disadvantages of the above two ways to create objects:

Although both of the above can create objects

But we don’t know what type the object we created is?

Of course we know they are of type OBject

At this time we need to use a custom constructor to create an object

3. Create an object with your own constructor

function Person(name,age,sex,like){

    console.log('No value is passed to the like parameter, it is undeined',like)

    // Here this refers to the Person object console.log('this',this)

    this.name=name;

    this.age=age;

    this.sex=sex;

    this.say=function(){

        console.log("My name is",name)

    }

}

//This line of code means creating an object//Instantiating an object at the same time//And initializing the properties of this object//So this line of code is not simple let per1=new Person('Conan',19,'男');

per1.say();

console.log(per1 instanceof Person);//true

Now we know that per1 is of type Person . This is the advantage of creating objects with custom constructors. We know what type of object it creates.

ps: Constructors usually start with a capital letter

When we create a new object, we do four things:

By creating a custom object, we understand that when we create a new object, we do four things:

• 1. Create space to store the current object
• 2. Set this to the current object
• 3. Set properties and methods
• 4. Return this object

4. Factory pattern creates objects

function createObj(name,age) {

    let obj = new Object();

    obj.name=name;

    obj.age=age;

    obj.sayHi=function(){

        console.log(obj.name)

    }

    return obj;

}

let per=createObj('司藤',200)

console.log(per.age); //200

per.sayHi(); //Si Teng

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