<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="-1">

For ASP pages use following script at the extreme beginning of the page

<% Response.CacheControl = "no-cache" %>
<% Response.AddHeader "Pragma", "no-cache" %>
<% Response.Expires = -1 %>

In case of JSP pages use following code

<%
response.setHeader("Cache-Control","no-cache");
response.setHeader("Pragma","no-cache");
response.setDateHeader ("Expires", -1);
%>

If you are generating your response in java or some other languages then you need to set following parameters in response header.

response.addHeader("cache-control", "no-cache");
response.addHeader("pragma", "no-cache");
response.addHeader("expires", "-1");

All of the above method works on the response of the particular page and tell browser not the cache the response.

There is another way of telling browser to make a fresh request and don’t use the cached content for the page if any. This is done by appending some random characters to requested url. Below is sample code

<script>
var url = "http://techpitcher.com";
url += "?preventCache="+ Math.floor(Math.random()*100000);
</script>

This will create a random url every time and won’t allow browser to use cache content.

To convert a number to string you can append an empty string or you can use toString() method. toString() method is not supported by older browsers.

var num = 30;
num = 30 * 5; // 150
str = num + ""; // or
str = num.toString();

String to number conversion

To convert a String to number, you can perform arithmetic operations like (*, / or -) such that it doesn’t alter the given string value. You might have noticed that I have not included ‘+’ in the above list this is because that JavaScript uses ‘+’ sign for string concatenation so adding ‘123′ + 0 will result into ‘1230′ and not 123. We can also user Number() function to perform the conversion. This is bit slower than any of the above options because this make explicit call to a function to perform conversion. But if you are using this option then it makes very clear that what your code is intended to do. So in my opinion if you are not worried about the performance then you can use Number() function as it will make code very clear.

var str = '123'
num = str * 1;
num = str - 0;
num = str/ 0;
num = Number(str);

If you try any of the above method on a text field which doesn’t contain valid numeric fields then you will get an ‘NaN’ as the result. So be careful

// check box
$("#check_box_id").attr("disabled", "disabled");
// radio button
$("#radio_btn_id").attr("disabled", "disabled");
// Text box
$("#text_box_id").attr("disabled", "disabled");
// button
$("#btn_id").attr("disabled", "disabled");

To Enable the input elements (checkbox, radio button, text box, button etc) , we need to remove disabled attribute. This can be done in the following way.

// check box
$("#check_box_id").removeAttr("disabled");
// radio button
$("#radio_btn_id").removeAttr("disabled");
// Text box
$("#text_box_id").removeAttr("disabled");
// button
$("#btn_id").removeAttr("disabled");

Another way of creating Array in JavaScript is
var secondArray = new Array(5);
This will create an Array of length 5.

Initializing an Array
You can initialize Array with pre defined data.
var dataArray = ['Tech', 'Pitcher', 'And', 'You'];

var result = Math.round(x * 100)/100;

And the output will be 10.57

function isValidDate(day, month, year){
var date;
//Get a Date object based on the given day, month and year
//months start at 0 (0-11 instead of 1-12)
date = new Date(year,month-1,day);
return ((day == date.getDate()) && (month == (date.getMonth()+1))
&& (year == date.getFullYear()));
}

When I started working on JavaScript, I felt it an easy language but sooner I was facing many issues like browser compatibility, memory leaks and many other common problems.
There are many sites discussing about all these. I would refer few of them in this post.

Being a scripting language, support of object-oriented programming is quite impressive. Even though there are no classes and instances, there are objects, prototypes, and implicit inheritance.
Browser compatibility issue can be handled using object level detection (Don’t check browsers rather check objects).
Memory leak is a challenging problem. The browsers try to work well with broken web, making it look fine and behave well. This is a very difficult task. If browser fails to collect the garbage that we left, is a buggy browser (memory leak). Most browsers don’t do a very good job about memory leak.

I would like to say thanks to Google and many other companies which are writing JavaScript libraries and making JavaScript hot. A good JavaScript Compiler would definitely make JavaScript library implementation easier. Check Google’s web development toolkit.
Mozilla’s (Venkman) JavaScript engine has built-in support for debugging, and thus can provide powerful tools for JavaScript developers.

Check following links

if one closure is buggy, then use more closures
http://www.bazon.net/mishoo/articles.epl?art_id=824

Memory Leaks

http://talideon.com/weblog/2005/03/js-memory-leaks.cfm

Javascript library
http://www.thingsthemselves.com/~jeff/computing/jslib/
http://www.howtocreate.co.uk/jslibs/

The Event Object
http://www.webdevelopersjournal.com/articles/jsevents3/jsevents3.html

Obejcts
http://developer.mozilla.org/

Google JavaScript APIs
http://code.google.com/apis.html

DISCLAIMER
This Blog includes links to other sites operated by third parties. These links are provided as a convenience to you and as an additional avenue of access to the information contained therein. I have not reviewed all of the information on other sites and are not responsible for the content of any other sites or any products or services that may be offered through other sites. If you are the owner of any of these links and have any objection please do let me know I’ll remove the link.