Mahesh Chandran Pillai. JavaScript is an implementation of the ECMAScript language standard and is typically used to enable programmatic access to computational

Mahesh Chandran Pillai

JavaScript is an implementation of the ECMAScript language standard and is typically used to enable programmatic access to computational objects within a host environment.

It can be characterized as a prototype-based object-oriented scripting language that is dynamic, weakly typed and has first-class functions


JavaScript is primarily used in the form of client-side JavaScript, implemented as part of a web browser in order to provide enhanced user interfaces and dynamic websites.


Put dynamic text into an HTML page React to events Read and write HTML elements Validate data Detect the visitor’s browser Create cookies


Access other resources such as Files, Databases and Programs

Talk to Web Servers Give similar output on different

browsers Be encrypted. Be used with copyrighted data or

algorithms


A script that is executed by the browser on a users computer

Instead of the entire page, part of the page is sent to the browser when user requests for the page.

Mostly run in response to an event For example: Click events, validations. Direct interaction with client


Requirements› A Text Editor like Notepad, Notepad++, etc….› Knowledge of basic HTML and form Tags

Ways for Including JavaScript in your HTML page› Direct Insertion

Using <SCRIPT> …….</SCRIPT> inside <HEAD> or <BODY> tags

› Embedded Insertion Using “Javascript” as prefix in other HTML tags. <input type=“button”

onclick=‘JavaScript:alert(“Hi”);’ />› External References

By specifying the “src” attribute in <SCRIPT> tag. <SCRIPT type=“text/javascript” src=“filename.js”/>


<html><head>

<title>JavaScript Skeleton</title><script type = "text/javascript">

// JavaScript can go here!// But no HTML!

</script></head><body>

<script type = "text/javascript">// JavaScript can go here too!// But no HTML!</script>

</body></html>


// - single line commenting /*…..*/ - multiple lines commenting <!- - // - - > - Commenting Javascript

from old browsers<script type = "text/javascript">


JavaScript is case-sensitive ƒ Ending statements with a semicolon is

optional. ƒ Open and Close braces for scoping

the embedded Java Script code is mandatory.

ƒ You can apply more than one script in a same HTML file.


Values, Variables, and Literals Expressions and Operators Regular Expressions Statements Functions Objects


JavaScript does not have explicit data types There is no way of specifying that a particular �

variable represents an integer, a string or a real.

All JavaScript variables are declared applying the keyword var.› For example: var x, y=7› Var x=“hello guys”› Y=true

JavaScript recognizes strings, numbers, Boolean values and null


Rules for identifiers Should start with a letter or an underscore (

_ ). Case sensitive. Numbers are possible in a

name.

Scope of variables Local variables: declared inside a function

using var keyword. Global Variables: declared outside the

functions.Mahesh Chandran Pillai

Operators:› » >=, ==, +=, ||, <, >, and so on.

Control statements:› If, if….else, for, and so on.

Keywords:› Var, true, false, new, return


if.. .. else› Syntax:if (condition){code to be executed if

condition is true}else{code to be executed if condition is not true}

if.. …else if…. else.if (condition1) { code to be executed } else if (condition2) { code to be executed } else { code to be executed }


Switch …. Case› Syntax:

switch(n) {case 1: execute code block 1 break ;case 2: execute code block 2 break ;default: code to be executed if n is different from case 1 and 2 }


For Loop› The for loop is applied when you know in

advance, how many times the script should run.

› For loop Syntax:var initval;for(initval=startvalue; initval<=endalue;

initval=initval+incrval) { code to be executed}


While › Syntax:

while (initval<=endvalue) { code to be executed}

Do..While › Syntax:

do { code to be executed } while (var<=endvalue)


For … in Loop› The for..in statement is applied to loop

(iterate) through the elements of an array or through the properties of an object.

› Syntax:for (variable in object) { code to be executed}


Functions can be of two types. Built in Functions

› Functions which are provided by Javascript. User Defined Functions

› A function is identified by the keyword function, followed by a programmer-supplied name for the function, and followed by a set of parentheses that optionally enclose data values needed by the function to carry out its processing.

› Syntax:function function_name(parameters) {

function-body; }


Calling Functions› You can call a function by using it name

followed by parenthesis with parameters if defined.Function_name(parameters);

› You can call functions with event handlers <Input type=“button” id=“Btn1" onclick=“fun1()“/>

› You can avoid functions by writing inline scripts It is useful only for avoiding small functions.


Alert( message)› Which puts a string into a little

announcement box (also called an alert box).› Syntax: alert(“I will show this message!");

Prompt(message, txtmsg)› which asks your visitor for some information

and then sets a variable equal to whatever your visitor types.

› Syntax: var name = prompt("What's your name?", "put your name here");

Confirm()› Which confirms the users action and returns a

Boolean value.› Syntax: confirm(“Do you want to continue”);



Examples: alert("Hello, world!");

prompt("Pls enter u r name", "enter here ");

confirm("Do you want to continue");

document.write (str)› This function will help you to write any

string message to the web page.


Date› The Date Object type provides a common set of

methods for working with dates and times. String

› The String Object type provides a set of methods for

› manipulating strings. Math

› The Math Object type provides a common set of methods for working with mathematical tasks.


Name Description

getDate() The day of the month as an integer from 1 to 31

getDay() The day of the week as an integer where 0 is Sunday and 1 is Monday

getHours() The hour as an integer between 0 and 23

getMinutes() The minutes as an integer between 0 and 59

getMonth() The month as an integer between 0 and 11 where 0 is January and 11 is December

getSeconds() The seconds as an integer between 0 and 59

getTime() The current time in milliseconds where 0 is January 1, 1970, 00:00:00

getYear() The year, but this format differs from browser to browser


substring(startIndex) substring(startIndex,endIndex) charAt(index) toLowerCase() toUpperCase() toString() valueOf() Indexof()


Name Description

exp() Value of e raised to the power passed as the argument

Abs() Absolute value of the

sqrt() Square root of the argument

round() Argument rounded up if its decimal value is greater than or equal to 0.5 and rounded down otherwise

pow() First argument raised to the power passed as the second argument

random() Random number between 0 and 1

min() Lower of the two numbers passed as arguments

Max() Higher of the two numbers passed as arguments

Log() Natural log of the argument

floor() Integer lower than or equal to the number passed as the argument

ceil() Integer greater than or equal to the number passed



Name Description

escape(string) Encodes a string from ASCII into an ISO Latin-1.

Unescape() encodes a string from ISO Latin-1 to ASCII

Eval() Converts a string to integer or float value. It can also evaluate expressions included with a string.

isNaN(value) If the value passed is a not a number, the Boolean value of true is returned, if it is a number, it returns false.

typeof operator This is an operator but its usefulness is similar to a function. This operator returns the type of the object it operates on.

parseInt() Converts a string to an integer returning the first integer encountered which is contained in the string.

parseFloat() Returns floating point numbers the same as the parseInt function, but looks for floating point qualified strings and returns their value as a float.

toString() Converts an object to a string

A collection elements in contiguous memory location.

Creating Arrays› Syntax

Var arr_name=new Array(elements);› Example

var colors = new Array("red", "orange", "yellow", "green", "blue", "indigo", "violet");

Assigning Valuesvar the_answers = new Array();the_answers[0] = "yes";the_answers[1] = "no“;


An associative array uses strings instead of numbers to store values.

Examples:var phone_book = new Array();phone_book[“devu"] = "(415) 555-5555";phone_book["info"] = "(415) 555-1212";

Length property of array will help you to find the number of elements.


onLoad onMouseOut and onMouseOver onReset onSelect onSubmit onUnload onAbort onBlur onChange onClick onError onFocus OnKeyup OnKeyDown OnKeyPress


Event handlers are functions are invoked when an event is raised or fired by the object.

Examples:› <a href = "#" onMouseOver = "alert(‘Mouse

overboard!');">board</a>› <a href = “hello.html" onClick = "alert('I\'m

glad you have JavaScript turned on!'); return false;">Click me</a>

› <a href = "#“ onClick = “var the_color = prompt('red or blue?',''); window.document.bgColor = the_color; return false;">change background</a>



The document object lists all the images, links, forms, and other stuff on a web page.

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Mahesh Chandran Pillai. JavaScript is an implementation of the ECMAScript language standard and is typically used to enable programmatic access to computational