Tuesday, March 20, 2012

Javascript essentials for beginners

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 Window.close( )- will close the window.

 Window.open( )- will opens a new window.

 Window.history. back()- will move the browser to previous window.

 Window.history. go(-2)- changes ur screen to 2 screen back.

 Window.history. forward() - will make the burron as Forward

 window.navigate( ) - method that also loads a document into a window,
but you can’t use it for crossbrowser applications.

 Math.random( )- will generates you a Random Numebr

 alert('Message goes here')- To generate an alert message

 if (confirm("Your question))- To generate an OK/Cancel box

 prompt('Prompt text','Suggested input')- To generate a user prompt

 navigator.appName – Gives Browser name

 navigator.cookieEna bled will give you true/false based on the
browser support for cookies. This property is read only.

 document.all. tags("input" );- will returns all “input” tags.

 All the variables declared between <script> and </script> tags that
are independent of any functions defined are initialized before *onLoad*()
function of the page. These are nothing but the *Global Variables*.

 <INPUT TYPE=IMAGE SRC=images/login1. GIF ALT=SignIn> - *makes an
Image act as a submit button*

 <body oncontextmenu= "return false">- will avoid right mouse popups.

function click() {if (event.button= =2) {alert('Disabled' )}}

document.onmousedow n=click

 Use the "size" parameter to the select tag. size=2, size=10- to get
the Scroll bar for Select.

 parent.frameName. print()- to print the contents of a different frame

if (window.navigator. userAgent. indexOf(' MSIE 6.0') != -1 &&
window.navigator. userAgent. indexOf(' SV1') != -1) {
i=35; //This browser is Internet Explorer 6.x on Windows XP SP2
} else if (window.navigator. userAgent. indexOf(' MSIE 6.0') != -1) {
i=60; //This browser is Internet Explorer 6.x
} else if (window.navigator. userAgent. indexOf(' Firefox') != -1 &&
window.navigator. userAgent. indexOf(" Windows") != -1) {
i=25; //This browser is Firefox on Windows
} else if (window.navigator. userAgent. indexOf(' Mozilla') != -1 &&
window.navigator. userAgent. indexOf(" Windows") != -1) {
i=45; //This browser is Mozilla on Windows
} else {
i=80; //This is all other browsers including Mozilla on Linux

------------ --------- --------- --------- --------- --------- -



function *isEnterKey* (evt) // Event object processor for NN4, IE4+, NN6


if (!evt)


evt = window.event // grab IE event object


else if (!evt.keyCode)


evt.keyCode = evt.which // grab NN4 event info


return (evt.keyCode == 13)


function *processOnEnter* (fld, evt)


if (isEnterKey( evt))


alert(“Ready to do some work with the form.”)

return false


return true




*document.** formObject. textObject*

Field 1: <INPUT TYPE=”text” NAME=”field1” onKeyDown=”return *processOnEnter

Field 2: <INPUT TYPE=”text” NAME=”field2” onKeyDown=”return *processOnEnter



Things however can get more complicated if you need the hyperlink click do
something other than redirecting the user to another page. For example, you
want to pop up a message, populate a field, syntax-check the user's input,
or other client-side tasks. You know, dynamic html (dhtml) stuff. Enter the
javascript:void( 0) function. I ran into this feature years ago while
searching for something, and I've been a loyal user ever since. The
javascript:void( 0) function basically neuters the hyperlink while allowing
you to carry out some dhtml activity within the onClick event, i.e.:

*<a href="javascript: void(0)" onclick="alert( 'You clicked.')" >www.abcd.com

The void() function causes the browser to take no redirection action upon
clicking. In most modern, javascript-literate browsers you can accomplish
the same disarming task by adding a "return false;" at the end of the
onClick event code, but you'd still need to provide something in for the
href property, so might as well make it javascript:void( 0).

------------ --------- --------- --------- --------- --------- -

*How do I change my mouse pointer with JavaScript*

Your mouse pointer (cursor) is just another element on a web page. You can
control many aspects of how it looks in response to different events on your
web page.

Let's say you have a form that takes a few seconds to process and you want
to let your users know not to keep clicking the "submit" button. You can
very simply add the following to the *<FORM>* HTML tag:

<FORM ... onsubmit="document. body.style. cursor='wait' ">

Here is a list of possible cursors you can use:





pointer (hand in IE 5.x)





e-resize, w-resize, n-resize, s-resize, ne-resize, nw-resize, se-resize,

------------ --------- --------- --------- --------- --------- -

*checking date format*

function isLeap(year) {
if(year % 400 == 0){
return true;
} else if((year % 4 == 0) && (year % 100 != 0)){
return true
} else return false;

function days_in(month, year){
if(month == 4 || month == 6 || month == 9 || month == 11){
return 30;
} else if(!isLeap(year) && month == 2){
return 28;
} else if(isLeap(year) && month == 2){
return 29;
} else return 31;

function checkDate(myItem) {
var myArrayDate, myDay, myMonth, myYear, myString, myYearDigit;
myString = myItem.value + "";
if (myString == "" || myString == "mm/dd/yyyy" ){
myItem.value = "mm/dd/yyyy" ;
return true;
myArrayDate = myString.split( "/");

myDay = Math.round(parseFlo at(myArrayDate[ 1]));
myMonth = Math.round(parseFlo at(myArrayDate[ 0]));
myYear = Math.round(parseFlo at(myArrayDate[ 2]));
myString = myYear + "";
myYearDigit = myString.length;

if (isNaN(myDay) || isNaN(myMonth) || isNaN(myYear) || (myYear < 1) ||
(myDay < 1) || (myMonth < 1) || (myMonth > 12) || (myYearDigit != 4) ||
(myDay > days_in(myMonth, myYear))){
alert("Please check your Date format. (mm/dd/yyyy) ");
myItem.value = "mm/dd/yyyy" ;
return true;
} else{
return false;

You can easilly change this script to check another date format by changing
the split method

*How can I disable the back button in a web browser ?*

We can use onLoad="if(history. length>0) history.go( +1)"

<a href="somwhere. asp" onclick="location. replace(this. href);return
false;">TEST< /a>


<meta http-equiv=refresh content="0, URL=page2.html" >

*Can I include JavaScript code from external JS files, rather than
embedding all my scripts within HTML pages? *

*Answer:* Yes. To do so, create a new file with the extension myscript.js.
Put your JavaScript code in this file; do not include opening and closing
SCRIPT tags in the myscript.js into your Web page, use these tags in your
HTML file: .js files containing JavaScript functions that you reuse on many
different HTML pages.

*Question: How do I code a select menu with hyperlinks to different pages?*




onChange="if( this.selectedInd ex!=0)

self.location= this.options[ this.selectedInd ex].value" >

<option value="" selected>Select a page

<option value="startpag. htm">JavaScript FAQ

<option value="numbers. htm">Numbers


value="strings. htm">Strings

<option value="navigati. htm">Navigation

<option value="colors. htm">Colors

<option value="http://www.javascripter.net/">JavaScripter. net



*Question: Can I make a button on my page work as a hyperlink to another
page? *

Top of Form

*Answer:* To create a button that works as a hyperlink you can use this


<input type=button

value="insert button text here"

onClick="self. location= 'Your_URL_ here.htm' ">


*Question: How do I disable a radio button in a form (making it not
selectable)? *

*Answer:* To make a radio button not selectable, in the button's INPUT tag
you can use an onClick event handler like this:

<INPUT type="radio" name="myButton" value="theValue"

onClick="this. checked=false;

alert('Sorry, this option is not available!') ">

Bottom of Form

*Question: How do I insert quotes in strings? *

*Answer:* Quotes in strings should be preceded by a backslash. This allows
the JavaScript interpreter to distinguish a quote within the string from the
quotes that serve as string delimiters. Here's an example:

string1='It\ 's five o\'clock!';

string2="<A HREF=\"index. htm\">";

Alternatively, if your string includes single quotes only, then you can use
double quotes as string delimiters, and vice versa. Here's an example:

string1="It' s five o'clock!";

string2='<A HREF="index. htm">';

*Question: Can I display an external HTML file as part of my page? *

*Answer:* Yes, you can display an external HTML file on your page by using:

 LAYER or ILAYER tags with SRC=FILENAME. HTM (in Netscape 4)

 IFRAME tag with SRC=FILENAME. HTM (in Explorer 4+ and Netscape 6)

In order to insert an external file, we called insertExternalFile( ) passing
the file name as a parameter. The function also takes two other parameters:
the width and height of the area where you'd like to display the inserted
file. Thus, each of the external files *inserted_file1. htm* and *
inserted_file2. htm* was embedded in the page using the following code:

insertExternalFile( "inserted_ file.htm" ,layer_width, layer_height)

The JavaScript code of the function insertExternalFile( ) is contained within
the HEAD section of the page:

<script language="JavaScrip t">


function insertExternalFile( fname,W,H) {

if (navigator.appName. indexOf(" Microsoft" )!=-1


navigator.appName= ="Netscape"

&& parseInt(navigator. appVersion) >4



document.write( ''

+'<IFRAME src="'+fname+ '" scrolling="no" frameborder= 0 border=0'

+(W==null ? '' : ' width='+W)

+(H==null ? '' : ' height='+H)

+'></IFRAME> '



if (navigator.appName= ="Netscape"

&& parseInt(navigator. appVersion) ==4) {

document.write( ''


+'<LAYER src="'+fname+ '" '

+(W==null ? '' : ' width='+W)

+(H==null ? '' : ' height='+H)

+'></LAYER>< /ILAYER>'






*Question:* How do I create a new layer from JavaScript?

*Answer:* Normally, you create layers by using DIV tags in the HTML source
code of your page. However, you can also create layers programmatically with
JavaScript! Here's an example:


<input type=button value="Create layer"

onClick="makeLayer( 'LYR1',200, 10,100,100, 'red',1,1) ">

<input type=button value="Delete layer"

onClick="deleteLaye r('LYR1') ">


function makeLayer(id, L,T,W,H,bgColor, visible,zIndex) {

if (document.layers) {

if (document.layers[ id]) {

alert ('Layer with this ID already exists!')



var LR=document. layers[id] =new Layer(W)

LR.name= id

LR.left= L

LR.top = T

LR.clip.height= H

LR.visibility= (null==visible || 1==visible ? 'show' :


if(null!=zIndex) LR.zIndex=zIndex

if(null!=bgColor) LR.bgColor=bgColor


else if (document.all) {

if (document.all[ id]) {

alert ('Layer with this ID already exists!')



var LR= '\n<DIV id='+id+' style="position: absolute'

+'; left:'+L

+'; top:'+T

+'; width:'+W

+'; height:'+H

+'; clip:rect(0, '+W+','+H+ ',0)'

+'; visibility:' +(null==visible || 1==visible ? 'visible':'hidden' )

+(null==zIndex ? '' : '; z-index:'+zIndex)

+(null==bgColor ? '' : '; background-color: '+bgColor)


document.body. insertAdjacentHT ML("BeforeEnd" ,LR)



*Question:* *Can I suppress JavaScript error messages?*

*Answer:* Yes. To suppress all JavaScript error messages on your HTML page,
you can put the following code fragment in the HEAD section of your page:

<SCRIPT language="JavaScrip t">


function silentErrorHandler( ) {return true}

window.onerror= silentErrorHandl er()



*I want to launch a new window, BUT the contents of the new window IS NOT an
HTML file or CGI script. It is rather, just "document.write" statments
executed by the parent window ?*

var handle = window.open( "", ...);


handle.document. open();

handle.document. write(... );

*How do I get a print preview window to display from JavaScript?*

<title>Print Preview</title>
function printpr()
var OLECMDID = 7;
/* OLECMDID values:
* 6 - print
* 7 - print preview
* 1 - open window
* 4 - Save As
var WebBrowser = '<OBJECT ID="WebBrowser1" WIDTH=0 HEIGHT=0
CLASSID="CLSID: 8856F961- 340A-11D0- A96B-00C04FD705A 2"></OBJECT> ';
document.body. insertAdjacentHT ML('beforeEnd' , WebBrowser);
WebBrowser1. ExecWB(OLECMDID, PROMPT);
WebBrowser1. outerHTML = "";
<input type='button' value="Print Preview" onclick="printpr( );">
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