Advanced Java Script (Ecma Script)

• Java Script is all about objects


• objects are all about properties


• Properties are all about attributes


• Primitive Wrappers


1. number ex: new number(125.25)
2. boolean
3. string(wrapper as a object and give methods and properties)


• Objects


1. Literal Form : var obj = {}
2. Constructor Form : var obj = new Object()


• Regex


1. Literal Form : / /
2. Constructor Form : new regExp()


• Array


1. Literal Form : [10,20]
2. Constructor Form : new Array[10,20]


• Iterate Object Properties
  Ex : for(var property in object)


• Private Variables
  Ex : var _name


• Variables with use by java script engine
  Ex : var _ _name_ _


• Change Invoker by using call,apply and bind methods.
  


• Object Properties


1. On Properties (Created Properties)
• Enumerable (can Iterate)
1. Data Properties
2. Accessor Properties
• Non Enumerable (can't Iterate)
1. Data Properties
2. Accessor Properties


2. Prototype Properties (Primitive values and references of objects)
• Enumerable (can Iterate)
1. Data Properties
2. Accessor Properties
• Non Enumerable (can't Iterate)
1. Data Properties
2. Accessor Properties


• Data Properties
  Can read and write or can prevent read and write both.
  Attributes
  
  1. Writable (readOnly : false , writeOnly : true)
  2. Writable should be false when there is a constant


• Accessor Properties
  Can give access to read only /write only / read and write both.
  Keep value in , EX : _name : "hffe"


• Property is a collection of set of attributes.


• Common Attributes
1. Configurable
   
   • true : Can Delete Property
   • false : Can't Delete Property
2. Enumerable
   
   • true : Appear when iterating
   • false : Doesn't appear when iterating


• Set attributes to properties
  EX : Object.getOwnDescriptor(myObj,"age");
• Create new property and replace
  EX : Object.defineProperty(myObj,"property",{descriptor});


• Stop adding of new properties to the object by using prevent extension
• Object.preventExtension(Array)
• Check the extension of the object
  object.isExtensible(Array);


• Seal Objects (Make configurable false)

Can't add or delete but can make changes.
object.seal(Array)
check whether object is sealed or not : object.isSealed(Array)

• Freeze (Writable false,read only)

object.Freeze()
Check whether object is writable or not : object.isFreezable()

• Constructor Function (First letter should be capital and use new key word.
  1. Create an object in heap
  2. Invoker
  3. Invoke
  4. Return object
  
  
  • EX: function Print(){
    console.log(this) // Print{}
    }
    var a = new Print(){};
    console.log(typeOf(a)); // object


• Replace new Property
  EX : Student.prototype = Object.create(Person.prototype);
  Link Student to the prototype
  Student.prototype.constructor = Student;