Javascript

JavaScript Tutorials is one of the best Quick reference to the JavaScript. In this JavaScript reference you will find most of the things about java script. JavaScript tutorial is classified into sections with examples. This tutorial is mainly for the beginners but experienced programmer can also learn many things from this JavaScript tutorial series. This JavaScript Tutorial will teach you the fundamentals of JavaScript programming, including the use of the core JavaScript objects and the syntax of the language like statements, conditionals, loops, functions, etc. You will also learn how to immediately put JavaScript to validate forms, calculate values, work with image rollovers and create other user interface. JavaScript is widely used scripting language for mainly validating the user input on the client side (browser). It is also used with the DHTML for creating interactive user interface design.

What is JavaScript? - Definition In this article you learn the basics of JavaScript and create your first JavaScript program. What is JavaScript? JavaScript is scripting language used for client side scripting. JavaScript developed by Netscape in 1995 as a method for validating forms and providing interactive content to web site. Microsoft and Netscape introduced JavaScript support in their browsers. Benefits of JavaScript Following are the benefits of JavaScript. •

associative arrays

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loosely typed variables

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regular expressions

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objects and classes

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highly evolved date, math, and string libraries

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W3C DOM support in the JavaScript

Disadvantages of JavaScript •

Developer depends on the browser support for the JavaScript

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There is no way to hide the JavaScript code in case of commercial application

Creating your first JavaScript Program In the first lesson we will create very simple JavaScript program and run in the Internet Explorer. This example simply displays "Welcome to JavaScript World!" message in the browser.

Test JavaScript program from here. Here is the code of JavaScript program: <script language="JavaScript"> function sayhello(){ alert("Welcome to JavaScript World!"); }

Click the following link to run your first java script example

Run JavaScript First Program

Writing Simple Java Script Program In this article you learn the basics of JavaScript and create your first JavaScript program. Creating your first JavaScript Program In the last lesson you learned how to create simple java script program. To run the program open the html file in any browser and click on the "Run Java Script First Program". The will display the message box. Here is the screen shot of the browser.

Test JavaScript program from here. Here is the code of JavaScript program: <script language="JavaScript">

function sayhello(){ alert("Welcome to JavaScript World!"); }

Click the following link to run your first java script example

Run JavaScript First Program

Following is the JavaScript program that will show the message: <script language="JavaScript"> function sayhello(){ alert("Welcome to JavaScript World!"); } The alert() function of the java script displays message.

JavaScript Statements In this article you learn the basics of JavaScript and create your first JavaScript program. JavaScript Statement The JavaScript language supported Two type Condition. 1.if statement 2.Function if Statement The if statement is used to make decisions in JavaScript. Boolean operators are also used in along with the if statement. The if statement is the most used features of JavaScript. It is basically the same in JavaScript as it is in other programming languages. Example <SCRIPT language="JavaScript">
document.write("Statement!
") } //--> my program successfully completed Function The function keyword identifies as a function. The parameters in the parenthesis ( ) provide a means of passing values to the function. There can be as many parameters separated by commas as you need. This is perfectly ok to have a function with no parameters. These parameters are variables which are used by the JavaScript statements inside the curly braces { }. The variable keyword is not needed to declare the parameters in a function as variables because they are automatically declared and initialized when the function is called. The function can return a value by using the return keyword. Example <script languane="JavaScript"> function prod(a,b) { var x=a*b return x; } var mul=prod(2,5); document.write("multipication:"+mul); Conditional JavaScript if-else Statement The JavaScript Conditional Statement used to different actions and used to based on different conditions. you want to execute some code if a condition is true and another code the condition is not true, use the if....else statement. Example script type="text/javascript"> var a = new Date() var time = a.getHours() if (time < 20)

{ document.write("Good morning!") } else { document.write("Good day!") }

JavaScript Variables and Data types In this article you will learn the basics of JavaScript Variables and Data types. JavaScript Variables .Every piece of data is known as a value. When a value is referred in a statement, it is called a literal value. For the same reason people are identified by names as opposed to "human" or "person", literal values can be named in order to make repeated reference to them practical, efficient and readable. These names are called variables. Declaring and Initializing the Variables var num // declare variable, has null value num = 20 // assign a value, null value is replaced //OR var num=20 // declare AND assign value (initialize) var a,b,c,d //multiple variables may be declared simultaneously var a = 5, b = 6, c = 7,d=8 //multiple variables may be initialized simultaneously Variable Names Variable names cannot contain spaces, begin with a number and can not be used the underscore (_) . JavaScript Variable name can not use any reserved keywords. The two words can either be separated by an underscore (my_variable) or (myVariable). Variable Scope There are two types of Variable scope:1. Globle scope Variable, 2 . Local scope Variable. 1.Globle scope Variable:- A variable declared or initialized outside a function body has a global scope, making it accessible to all other statements within the same document. 2. Globle scope Variable:- A variable declared or initialized within a function body has a local scope, making it accessible only to statements within the same function body. [NOTE:- If a variable is initialized inside a function body but the var keyword is left off, the variable has a global scope and is only accessible after the function containing it is invoked. It is safer to always use the var keyword ]

Java script Data type Data Type:- A data type is defined by the value assigned to it . A variable could be a number on one line, then assigned a string value and later be assigned an object reference. JavaScript would change its data type dynamically .It also represent the data's nature. Data is directly treated on those data types and calculate up on the works . There are two types of the data types, As follow:1.Primitive data types 2.Compositive data types 1.Primitive data types:- Primitive data types are the simplest building blocks of a program. There are following types :•

numeric:-JavaScript supports both integers and floating point numbers .Integers are whole numbers and it does not support the decimal numbers .Such as : 145 . Floating point numbers are fractional numbers or decimal numbers . Such as : 12.50

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string:- String is a collection of characters enclosed in either single quotes and double quotes .If the string starts with a single quotes and it must end with single quotes .If the string starts with a double quotes and it must end with double quotes . Such as : 'Welcome to JavaScript' or "Welcome to JavaScript".

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Boolean:-Boolean literals are logical values that have only one of two values, true or false. It used to conditional sanitations. Our statements are checked true or false then we use the Boolean variables.

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null:-The null value represents no value that means strings are empty .

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undefined:- A variables to be declared but given no any initial value then it runtime error display

Example for :-This example is represent the sum of two floating numbers and print the messages in single quotes and double quotes. <script language="javascript"> function showAlert() { var a=200.40; var b=10.50; var sum=0; sum=a+b; document.write(" sum= "+sum); document.write("\t\tHello\nworld!\n"); document.write('\nWelcome to JavaScript'); } <script language="javascript">

showAlert(); This program is used to Boolean expression and it display the numbers between 1 to 500 and if user to not enter the number then it display the you did not enter any number. <script type="text/javascript"> var n=0; n=prompt("Enter a number"); document.write("Your entered number is :"+n); if (n>=1 && n<10) document.write("Your entered number is greater than 1 and less than 10"); else if(n>=10 && n<20) document.write("Your entered number is greater than 10 and less than 20"); else if(n>=20 && n<30) document.write("Your entered number is greater than 20 and less than 30"); else if(n>=30 && n<40) document.write("Your entered number is greater than 30 and less than 40"); else if(n>=40 && n<100) document.write("Your entered number is greater than 40 and less than 100"); else if(n>=100 && n<=500) document.write("Your entered number is greater than 100 or less than 500"); else document.write("You did not enter any number!")

String Number Operations in JavaScript In this article you learn the basics of JavaScript and create your first JavaScript program.

What is String Number Operation? The JavaScript String is a loosely type language. This is not mean that it has no data types that the value of a variable or a JavaScript object property does not need to have a particular type of the value assigned, or that it should be always hold the same type of value. JavaScript also freely type-converts values into a type require by the context of their use. JavaScript being is the loosely typed and willing to type-convert still does not save the programmer from need to the think about the actual type of values that they are dealing with. A very common error in browser scripting. for example, it is to read the value property of a form control into which the user is expected to type a number and then add that value to another number. Because the value properties of form controls are strings if the even then character is sequence they contain represents a number of the attempt to add that string to a value, even if the value happens to be a number, results in the second value being type-converted into a string and concatenated to the end of the first string value from the from control. The problem arises from dual nature of the + operator used for the both numeric addition and string concatenation. which the nature of the operation performed is determined by the context, where only both the operation are numbers to start with the + operator perform addition. Otherwise it converts all of its operands to strings and does concatenation. Converting String: The String most often from the action + Operators. when one of its operators not a number. The easy way of getting the string that results from type-conversion is to concatenate a value to string. The alternative method of convert a value into a string to pass it is argument to the String constructor called as a function. Exam:Var string Value= String(d); Converting Number: The Converting values to numbers especially to strings numbers, it is an extremely common requirement and many methods can be used. There are any mathematical operation except the concatenation addition operator will force type-conversion. So the conversion of a string to a number might entail performing a mathematical operation on the string representation of the number that would not affect the resulting number, such as subtracting zero or multiplying by one. var numValue = stringValue - 0; var numValue = stringValue * 1; var numValue = stringValue / 1; String in JavaScript The JavaScript language until now we have been focusing on the language constructs of JavaScript: if statements, loops, functions, etc. This primer are going to take a step back and cover the inner workings of some of the native JavaScript objects: Strings, Numbers and Arrays. Example:

<Script language="JavaScript"> document.write(' Test'.indexOf('T')); document.write('This '.lastIndexOf('T')); document.write('This is test'.charAt(10)); document.write('This program Test'.length); document.write(' program'.substring(1, 10)); document.write('my exam Test'.substr(7, 10)); document.write('my program'.toUpperCase()); document.write(' first JavaScript program'.toLowerCase()); document.write("
") Array in JavaScript Array is the basically just a list of items. Each item an array can be whatever you want, but they are usually related to one-another. Example: <script language="JavaScript"> var students = ['amar', 'rani', 'vinod', 'susil','santosh']; var suffixes = ['1st', '2nd', '3rd', '4th','5th']; for(var i=0; i<=4; i++) { alert('The '+suffixes[i]+' student is '+students[i]); } JavaScript in Number Operation The numbers is a central task for the many programs. In fact, the desire to automate number operations was the motivation that drove the invention of digital computers decades ago. we will learn how to work with numbers in Java, including arithmetic, conversions, and other numeric operations.

Example: <Script language="JavaScript"> var sum = 10 + 10; sub = 15 - 5; mul = 25 * 5; //multiplication divided = 30 / 5; modulus = 10 % 10; //modulus division document.write("sum:"+sum ); document.write("sub:"+sub); document.write("mul:"+mul) ; document.write("divided:"+ divided); document.write("modulus:"+ modulus);

Conditional Examples(if - else- switch case) in JavaScript In this article you will learn the basics of JavaScript conditions and create your conditional examples in JavaScript . About Conditional Statement First of all we write the code after that we want to perform the different actions for different decisions. We can use conditional statements in our code. Conditional statements in JavaScript are used to perform different actions based on different conditions. There are following types of Conditional Statements:•

if statement:- It means the condition is true then our writing code is executed other wise our code is not execute . Syntax for the if statement:if ( expression ) {

statement1 statement2 } •

if - else statement:- This statement is used to when the condition is true then our code to execute and when the condition is false then our written code is not execute. Syntax for the if - else statement:if (expression) statement1 else if (expression2) statement2 else statement3

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if...else if....else statement -This statement is used to if you want to select one of many blocks of code to be executed .

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switch statement:-This statement is used to if you want to select one of many blocks of code to be executed. Syntax for the switch statement:switch (expression) { case1: statement1 break case2: statement2 break default: statement3; }

This example is if - else statement. It display the first of all the sum of two numbers and check the condition after that it execute the code. <script language="javascript"> function showAlert() { var a=20; var b=10; var sum=0; sum=a+b; document.write(" sum= "+sum); if(sum==3) { document.write("Condition is true"); document.write("This is my first if statement program"); } false

{ document.write("Condition is false"); document.write(" This is my first if -else statement program"); } } <script language="javascript"> showAlert(); This example is display to all months in a year for using the switch case: <script type="text/javascript"> var n=0; n=prompt("Enter a number between 1 to 12:") switch(n) { case(n="1"): document.write("January"); break case(n="2"): document.write("Febuary"); break case(n="3"): document.write("March"); break case(n="4"): document.write("April"); break case(n="5"): document.write("May"); break case(n="6"): document.write("June"); break case(n="7"): document.write("July"); break case(n="8"):

document.write("August"); break case(n="9"): document.write("September"); break case(n="10"): document.write("October"); break case(n="11"): document.write("November"); break default: document.write("December"); break }

Conditions In Java Script In this article you learn the basics of JavaScript and create your first JavaScript program. About JavaScript Java Script is Netscape's Cross - platform, Object - based Scripting language for Client and Server applications. It is a Case sensitive application. JavaScript programs are usually embedded directly in HTML files. The script executes when the user's browser opens the HTML file. JavaScript is different from the Java language. Now the biggest problem is the imperfect JavaScript implementations that today's browsers offer. Although all major browsers that are version 3.0 or higher include JavaScript code support, they deal with JavaScript differently. In fact, different versions of the same browser handle JavaScript differently. This makes it difficult to create a complicated JavaScript code that work across all browsers. So always check your pages on as many different browsers (and even platforms) as possible. The Simple Example to display the Sum of two Digits : <script language="javascript"> function showAlert() { val1=20; val2=10; document.write("sum="+(val1+val2)); }

<script type="text/javascript"> showAlert(); JavaScript code is embedded in HTML within a <SCRIPT> tag. It can be used to any number of JavaScript Statements. showAlert() is a function to use in JavaScript language. Val1 and Val2 is a data type. we take the value 20 and 10 in val1 and val2. Document.write is also a function to use print the Message and values. The result is 20 display on the Screen.

Looping In Java Script In this article you learn the basics of JavaScript and create your first JavaScript program. What is JavaScript loop? The JavaScript loops used to execute the same block or code a specified number of times and while a specified condition. JavaScript loops Very often write code, you want the same block of code to run over and over again in a row. The Instead of adding several almost equal lines in a script we can use loops to perform a task. JavaScript supported Two different type looping :1.The For Loop 2.The while Loop For Loop: The JavaScript for loop is used the know in advance how many times of the script should run. JavaScript loop Use a For loop to run time same block of code a specified the number. Example: <script language="javascript"> var i=0 for (i=0;i<=6;i++) { alert("The number is " + i) }

The while Loop: The while loop is used when the loop to execute and continue executing while the specified condition <script language="Javascript"> var i=0 while (i<=10) { document.write("serial number" + i) document.write("
") i=i+1 } . The do while loop The JavaScript do...while loop is a variant of the while loop. The loop will be always execute a block of code once and then it will repeat the loop as long as the specified condition is true. This loop will be always executed once, even if the condition is false, because the loop code are executed before the condition is tested. Example: <script language="Javascript"> var i=0 do { alert("number" + i) i=i+1 } while (i<3) The for in: This is not same as the for loop . The javascript for...in loop is used to provide to the enumerate

properties of a JavaScript object . This loop only found in JavaScript . This statement in the loop are executed for each property of an object until every property has been accessed. Example: <Script language="Javascript"> var i; var num= new Array(8,4,5,7,10); for(i in num) { document.write(" " ,num[i]); document.write("
") } Javascript looping Break and continue There are two statements supported in javascript used in loop:- Break and continue Break: The JavaScript break command will break the loop and continue executing the code the follows after the loop. Example: <Script language="Javascript"> var i=0 for (i=0;i<=6;i++) { if (i==3){break} alert("number" + i) } Continue: The JavaScript continue command will be break the current loop and continue with the next value. Example <script language="JavaScript">

var i=0; for (i=0;i<=8;i++) { if (i==4){continue} document.write("value" + i) document.write("
") }

JavaScript Functions In this article you will learn about the JavaScript functions. What is JavaScript Function? Java script Function is nothing but it is a reusable code-block that is execute when the function is called. Function is defined in the head section of the code. The syntax of JavaScript function is as follows: function fname(prameter1,parameter2, ...) { JavaScript code 1 JavaScript code 2 .... } While defining JavaScript function its important to remember that the keyword function should be in lowercase other wise JavaScript won't understand it as function. If you write function in uppercase the code will generate error. In the JavaScript semicolon is optional but its better to put semi-colon as part of best practices. All the java script code are written inside the curly braces. Example:

<script language="javascript"> function showmessage(){ alert("How are you"); }

Function starts with the function keyword and code of the function is enclosed in {..} brackets. Functions are written inside the head section of the html document, because function does not execute when the page loads. The alert function displays the message "How are you", when you clicked on the button ("Click Here")..

To test the program click here. What is the use of JavaScript Functions: The java Script Function is very useful in writing the JavaScript code. It is used to group many JavaScript codes under one name. For example you can write a function to validate email address. Built-in functions JavaScript provides many built in functions that ease the development of JavaScript programs. Here are the list of the built-in JavaScript functions: JavaScript Build in Function alert()

Function Description The alert() built-in function displays the

confirm() focus()

alert dialog box. The confirm() built-in function display the confirmation dialog box. and ask the user to determine from the two option . The focus() built -in function built the pointed object active and put the curser on the text field.

indexOf() prompt() select() write()

The prompt() built -in function display the prompt dialog box. Inquiring the user for input. The select() built -in function used to select the pointed object. The write() built in function used to write something on the document.

Function arguments: Through variable you can pass argument to function. The out put of the function looks on the arguments given by you . Example: <script language="javascript"> function myfunction(text) { confirm(text) }