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M. Taimoor Khan [email protected] Javascript Objects. Javascript Objects. Every data-type defined in Javascript is an object It has a class definition for it, unlike the basic data types

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M taimoor khan taimoorkhan@ciit attock edu pk

M. Taimoor Khan

[email protected]

Javascript Objects


Javascript objects
Javascript Objects

  • Every data-type defined in Javascript is an object

  • It has a class definition for it, unlike the basic data types

  • It allows the variables (objects) to make use of the built-in properties and functions defined for them

  • For example Number, String, Date, Array etc


User defined objects
User defined objects

  • Along with the built-in object types, the users can also define their own type of objects.

  • They are defined with some data members and member functions

  • Unlike classes in other programming languages, each object has to be re-defined with their own set of attributes and behavior

  • However, an object can be assigned to another object to get the same structure and values


Example
Example

<script type=“text/javascript”>

var person=new Object();person.firstname="John";person.lastname="Doe";person.age=50;person.eyecolor="blue";

</script>


Creating objects with constructor
Creating objects with constructor

<script type=“text/javascript”>

function person(firstname, lastname, age, eyecolor)

{

this.firstname = firstname;

this.lastname = lastname;

this.age = age;

this.eyecolor = eyecolor;

}

//Creating objects of type person

var p1 = new person(“John”, “Doe”, 50, “blue”);

var p2 = new person(“Sally”, “Rally”, 48, “green”);

</script>


Adding member functions
Adding Member Functions

<script type=“text/javascript”>

function person(firstname,lastname,age,eyecolor){this.firstname=firstname;this.lastname=lastname;this.age=age;this.eyecolor=eyecolor;this.changeName=changeName;function changeName(name){this.lastname=name;}

}

p1 = new person(“John”, “Doe”, 50, “blue”);

//The member function changeName() changes the lastname of the object person

p1.changeName(“David”);

</script>



Arrays
Arrays

<script type=“text/javascript”>

varmyCars=new Array("Saab","Volvo","BMW");

//array data members

var total = myCars.length;

//member functions to get index of value

vary=myCars.indexOf("Volvo");

//if the given value is a number or has alphabets

if(isNaN(myCars[1]));

//convert array items into a comma separated string

varallCars = myCars.join();

document.write(“<p>” + allCars + “</p>”);

</script>


<script type=“text/javascript”>

varmyCars=new Array("Saab","Volvo","BMW");

//push an item at the end of the array

myCars.push(“Toyota”);

//Pop an item from the end of an array

myCars.pop();

//remove an item from the start of the array

myCars.shift();

//convert array items into a comma separated string

varallCars = myCars.join();

document.write(“<p>” + allCars + “</p>”); //js use + to concate

</script>


<script type=“text/javascript”>

varmyCars=new Array("Saab","Volvo","BMW");

varotherCars = new Array(“Toyota”, “Honda”, “Suzuki”);

// concate two arrays into one

vartotalCars = myCars.concate(otherCars);

//reverse the order of the elements in the array

myCars.reverse();

//get second and third items from the array

varmoreCars = myCars.slice(1,3);

//sort the array alphabetically

myCars.sort();

</script>


<script type=“text/javascript”>

varmyCars=new Array("Saab","Volvo","BMW");

// add more items into the array

myCars.splice(2,0,“Ford",“Nissan");

//get a comma separated string of array items

var cars = myCars.toString();

</script>


Date object
Date object

<script type=“text/javascript”>

//instantiating date type objects

varcurrDate = new Date();

varsomeDate = new Date(milliseconds) //since 1970/01/01

varotherDate = new Date (“2014/02/28”); //date string

varanotherDate = new Date(year, month, day, hours, mins, seconds, milliseconds);

//Date objects can be compared using relational operators <,>,= etc.

</script>


Date member functions
Date member functions

<script type=“text/javascript”>

VarmyDate = new Date();

document.write(myDate.getFullYear);

document.write(myDate.getTime);

document.write(myDate.getDay);

</script>


Math object
Math Object

<script type=“text/javascript”>

//Math object has data members and member functions for mathematical relations

document.write(“<p>”+ Math.PI + “</p>”);

//Note: Javascript is case-sensitive math.pi is not the same as Math.PI

document.write(“<p>”+Math.round(2.39)+“</p>”);

//generates a random number between 0 and 1

document.write(“<p>”+Math.random()+“</p>”);

//Get Maximum Value

Document.write(“<p>”+Math.max(5,10,15,2,43,16) + “</p>”);

//Get Minimum Value

document.write(“<p>”+Math.min(5,10,15,2,43,16) + “</p>”);

//Get Square root

Document.write(“<p>”+Math.sqrt(16) + </p>”);

</script>


String objects
String Objects

<script type=“text/javascript”>

var venue = “attock”;

//get a character at the given index

document.write(“<p>”+venue[3]+”</p>”);

//length of string

document.write(“<p>”+venue.length+”</p>”);

varind = venue.indexOf(“t”); //index of characters match first found

var ind2 = venue.lastIndexOf(“t”); //index of characters match last found

var word = venue.match(“ock”); //returns the match term if found or null

venue.replace(“oc”, “zz”); //replace characters in 1st parameters with 2nd

venue.toUpperCase(); //convert string to upper case

venue.toLowerCase(); //convert string to lower case

</script>


<script type=“text/javascript>

//convert the string to array splitting on given term

var venues = “attock:wah:islamabad:lahore”;

varallVenues = venues.split(“:”);

</script>

//Other String functions

charAt(), concat(), search(), slice(), substr(), substring(), trim(), valueOf()


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