1. JavaScript Objects and
Functions
Dhananjay Kumar [@debug_mode]
Delhi Chapter Lead
Microsoft MVP
Mindcracker MVP
Telerik Evangelist
http://debugmode.net
FB: Dhananjay.25july@gmail.com

2. JavaScript Objects
• There are three ways you can create JavaScript Objects
JavaScript
Objects
Using Literals
Using New
Operator
Using
Object.Create()

3. JavaScript Objects
Using Literals
var student
= {
name: "dj",
grade : "z"
};
var studentName = student.name;
alert(studentName);
Object literal is an expression
It creates new object each time it appears
in the code
A single object literal can create many
objects in loop

4. JavaScript Objects
Using new operator
var student = new Object();
var studentArray = new Array();
new operator creates a new object
new operator initialize created
object also
new operator invokes a function as
give in above code snippet.
Function invoked after new
operator is Constructor

5. JavaScript Objects
Using Object.Create()
var student = Object.create(
{
name: "dj",
grade: 10
}
);
It is a static function
It always has two parameters
• Prototype
• Properties

6. JavaScript Objects
• There are three ways you can test Properties of JavaScript Objects
JavaScript Objects
Properties
in operator
hasOwnProperty()
method
propertyIsEnumerable()
method

7. JavaScript Objects
in operator
var student = Object.create(
{
name: "dj",
grade: 10
}
);
var studentProperty = "name" in
student
alert(studentProperty);
in operator returns true for own property
in operator returns false if there is no
property with given name
in operator returns true for inherited
property

8. JavaScript Objects
hasOwnProperty() method
var student =
{
name: "dj",
grade: 10
};
var studentProperty =
student.hasOwnProperty("name");
alert(studentProperty);
hasOwnProperty() method returns true
for own property
hasOwnProperty() method returns false if
there is no property with given name
hasOwnProperty() method returns false
for inherited property

9. JavaScript Objects
propertyIsEnumerable () method
var student =
{
name: "dj",
grade: 10
};
var studentProperty =
student.hasOwnProperty("name");
alert(studentProperty);
propertyIsEnumerable () method returns
true for own property which is
enumerable
propertyIsEnumerable () method returns
false if there is no property with given
name
propertyIsEnumerable () method returns
false for inherited property

10. JavaScript Objects
• Deleting Properties : using delete operator
Delete operator
returns
true if
successfully
deleted
If there is no
effect on
operation

11. JavaScript Objects
Deleting properties
var student =
{
name: "dj",
grade: 10
};
var result = delete student.grade;
alert(result);
var result1 = delete student["grade"];
alert(result1);
 It deletes object’s own property
 It does not delete inherited property. For example you cannot
delete property of student prototype or object it is inheriting
from.

12. Associative Array
Associative Array : Java
Script Array can be worked
with string index
var arrayofStudent = [];
var student1 = [];
student1["rollnumber"] = 19;
student1["name"] = "John";
student1["grade"] = "A";
arrayofStudent.push(student1);
console.log(arrayofStudent[0]["name"]);
Associative Array is that we can not traverse through array
elements in a loop.

13. JavaScript object as Associative Array
var student =
{
name: "dj",
grade: 10
};
for (i = 0; i < 10; i++) {
student["marks" + i] = 100 * i;
}
alert(student.marks8);
In Square bracket you
provide property name as
string. String is data type so
can be manipulated at run
time.
With dot you provide
property name as identifier.
Since they are not a data type
so cannot be manipulated at
run time.

14. For-in loop in JavaScript

15. Functions in JavaScript
var display_message = function
(age) {
alert("you are " + age +
"year old ");
};
display_message(19);
JavaScript
Functions
Named
Function
Anonymous
Function

16. Functions in JavaScript
 You can store it in a variable
You can pass it as parameter of
other function
You can use it in an expression

17. Functions in JavaScript
Pass by Value
var greetingmessage = "Hey DJ";
function showmessage(greetingmessage)
{
greetingmessage = "I am changing
value";
}
showmessage(greetingmessage);
alert(greetingmessage);
Pass By Reference
var arrayofname = ["dj"];
function showmessage(arrayofname) {
arrayofname[0] = "dhananjay";
}
showmessage(arrayofname);
alert(arrayofname[0]);

18. Functions in JavaScript
Nested Functions
mainfunction(7, 6);
function mainfunction(a, b) {
alert(a);
nestedfunction(88);
function nestedfunction(c) {
alert(b);
};
};
 Nested function can access variable of parent function
 Parent function cannot access variable of nested function

19. Functions in JavaScript
Namespace in JavaScript
Global if defined outside
any function
Local to function and all
nested function , if
defined in function
var MyModule = {
//code for module here
GetData: function () {
var student =
{
name: "dj",
grade: 10
};
var nameisobjectofstudent = "toString" in student;
alert(nameisobjectofstudent);
}
};

20. Functions in JavaScript
Namespace in JavaScript
Global if defined outside
any function
Local to function and all
nested function , if
defined in function
var MyModule = {
//code for module here
GetData: function () {
var student =
{
name: "dj",
grade: 10
};
var nameisobjectofstudent = "toString" in student;
alert(nameisobjectofstudent);
}
};

21. Functions in JavaScript
Namespace in JavaScript
Global if defined outside
any function
Local to function and all
nested function , if
defined in function
var studentObject =
{
name: "dj",
marks: 89,
findgrade: function (marks) {
if (marks > 75) {
return "Grade A ";
}
else {
return "Grade B ";
}
}
}
var grade = studentObject.findgrade(99);
alert(grade);

22. Functions in JavaScript
 It takes a function as argument
 It returns a function as output.

23. Functions in JavaScript
JavaScript function
Does not do any type checking
on argument values
Does not do any checking on
number of arguments passed
JavaScript function can be called
1. With exact number of
arguments
2. With more number of
arguments than specified
3. With less number of
arguments than specified

24. Functions in JavaScript
Less Number of Arguments

25. Functions in JavaScript
Less Number of Arguments

26. Functions in JavaScript
Less Number of Arguments
Handling undefined

27. Functions in JavaScript
More Number of Arguments