Try the below script and click on fun2 button. Button inside label tag have some problem, that is the second button invokes the onclick of the first button and then the second button.
Now remove the label (begin and end) tag and try the same code. Everything would work fine.
Tuesday, May 17, 2011
Tuesday, May 10, 2011
Simple javascript optimizations
Let us see some of the most simple javascript scripts optimizations which can make big difference,
Rule: Consider using local variable instead of global variable.
Rule: Avoid using eval() or function constructor.
Rule: Pass function, not string to setTimeout() and setInterval(). Passing stirng is same as calling eval().
Rule: Avoid using with().
For-in loop vs for loop
Slow:function forinloop()
{
var count=10000;
var arr=new Array();
for(var i=0;i<count;i++)
{
arr[i]=i;
}
var value=0;
for(var index in arr)
{
value+=arr[index];
}
}
Faster:function forloop()
{
var count=10000;
var arr=new Array();
for(var i=0;i<count;i++)
{
arr[i]=i;
}
var value=0;
count= arr.length;
for(var index=0;index<count;index++)
{
value+=arr[index];
}
}
Rule: Avoid using for-in loop, instead use for() loop.
String concatenation vs array join
Slow:function stringcat()
{
var count=10000;
var str="";
for(var i=0;i<count;i++)
{
str+="first,";
}
}
Faster:function arrayjoin()
{
var count=10000;
var arr=new Array();
for(var i=0;i<count;i++)
{
arr[i]="first";
}
var str=arr.join("");
}
Rule: Avoid string concatenation and use array join. The performance difference in significant only in IE 7.
Inbuilt functions vs primitive operations
Slow:function mathmin()
{
var count=10000;
for(var i=0;i<count;i++)
{
var a=10;
var b=5;
var min = Math.min(a, b);
}
}
Faster:function primitiveop()
{
var count=10000;
for(var i=0;i<count;i++)
{
var a=10;
var b=5;
var min = a < b ? a : b;
}
}
Rule: Avoid function calls, try to use primitive operations. The performance difference in significant only in IE 7.
External function vs inline function
Slow:function minfunction(a,b)
{
var min = a < b ? a : b;
return min;
}
function externalfunction()
{
var count=10000;
for(var i=0;i<count;i++)
{
var a=10;
var b=5;
var min=minfunction(a,b);
}
}
Faster:function inlinefunction()
{
var count=10000;
for(var i=0;i<count;i++)
{
var a=10;
var b=5;
var min = a < b ? a : b;
}
}
Rule: Avoid external function calls, try to use inline functions. The performance difference in significant only in IE 7.
Comments in the script
Slow:function withcomments()
{
var count=50000;
for(var i=0;i<count;i++)
{
/* dummy comments */
/* dummy comments */
var a=10;
/* dummy comments */
/* dummy comments */
var b=5;
/* dummy comments */
/* dummy comments */
var min = a < b ? a : b;
/* dummy comments */
}
}
Faster:function withoutcomments()
{
var count=50000;
for(var i=0;i<count;i++)
{
var a=10;
var b=5;
var min = a < b ? a : b;
}
}
Rule: Avoid comments in performance critical script. The performance difference in significant only in IE 7.
Try catch in performance critical functions
Slow:function withtrycatch()
{
var count=50000;
for(var i=0;i<count;i++)
{
try
{
var num=parseInt("10");
}
catch(e)
{
//handle exception
}
finally
{
}
}
}
Faster:function withouttrycatch()
{
var count=50000;
for(var i=0;i<count;i++)
{
var num=parseInt("10");
}
}
Rule: Avoid using try catch inside performance critical function.
Monday, April 25, 2011
Search Engine Optimization (SEO)
Developing a website or web application which can be indexed by search engine is very critical and it is called searching engine optimization of the website or web application.
Before starting the optimization let us look at some of the basic rules to be followed
Rule: Focus on the originality and quality of the content of your website.
Rule: Remember your ultimate consumers are your users, not search engines.
Rule: Original content is ranked high in the search result page.
Rule: Increasing the traffic to your website is more important than the rank of the page in the search result.
Rule: Perform any kind of optimization only to improve the user experience.
Below are some of the critical optimization rules
Rule: Use brief, but descriptive title in "title" (<title>Search engine optimization<title/>) tag. Choose a title that effectively communicates the topic of the page's content.
Rule: Create unique title for each page of the website.
Rule: Google search engine does not use keywords "meta" tag (<meta name="keywords" content="search engine optimization, indexing, optimization, rules" />) for indexing.
Rule: Provide crisp and clear description of the webpage in the description "meta" tag (<meta name="description" content="Critical rules for search engine optimization." />). Also provide unique description for each page of the website.
Rule: Use | (pipe) or - (hyphen) as separator and not _ (underscore) in "title" tag and description "meta" tag.
Rule: Provide URLs with readable text (e.g. http://codingrules.blogspot.com/2010/06/unit-testing.html) or keywords to access a webpage and not auto generated text or numbers (e.g. http://codingrules.blogspot.com/2010/06/20006.html).
Rule: Regularly check for broken links and remove the same.
Rule: Provide naturally flowing hierarchy for navigation and text for navigation. Avoid drop down menu, images or animation for navigation.
Rule: Provide site map for the user.
Rule: Submit your website's site map (xml format) with Google's webmaster tools for search engine to index your website. Generate XML site map for your website from http://www.xml-sitemaps.com/. Also Google's webmaster tools help webmasters better control how Google interacts with their websites and get useful information from Google about their site.
Rule: Provide custom 404 page, which can guide user back to a working page.
Rule: Write easy to read text content. Avoid images for textual content.
Rule: Try to use words and phrases on the webpage which the user would be looking for.
Rule: Use descriptive anchor text for links.
Rule: Format links to make it easy for users to distinguish between regular text and the anchor text of links.
Rule: Links on your page maybe internal—pointing to other pages on your site—or external—leading to content on other sites. In either of these cases provide descriptive anchor text for better user experience. Anchor text is the clickable text that users will see as a result of a link,
and is placed within the anchor tag <a href="..."></a>.
Rule: Do not design you entire webpage (or website) as image. Provide some text on the webpage which can be indexed by search engines.
Rule: Use descriptive name for images and not like "img1.png" or "pic.png".
Rule: Provide "alt" and "title" attribute text in the "img" tag (<img alt="" title="" src="" />).
Rule: Use "heading" tags (h1 to h6) to emphasize important text.
Rule: If the company name or the website name is embedded as image, then make sure the same is made available as text in the webpage (e.g. "title" tag or description "meta" tag etc).
Rule: For webpages with photo gallery, apart from providing image "alt" and "title" text, let the users to provide comments, which will increase the textual content of the webpage. But make sure to moderate the user comments.
Rule: User comments section can improve the textual content of the webpage. Moderate the user comments to avoid spam content.
Rule: Provide "Related links" section of links with in your website to increase the traffic to your website.
Rule: Provide complete address of your company on the website either on one of the webpage or on all the pages.
Rule: Use the company/product/service information, where ever applicable, instead of using we or our.
Rule: Use Google places, Videos, Images, Facebook, Twitter, etc for promoting your website.
Watch the below videos for more on SEO.
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