Posts Tagged ‘ Javascript ’

JavaScript: Edit web page in browser

Saturday, September 13th, 2008 By Nikhil

Well , I must say, not such an usefull piece of science, but if you are a Web Developer, might come handy , someday ( or will it?). Here is small bookmarklet, which allows to edit the web page for any site .
And Sorry!  You can save the results on your local machine only.

javascript:document.body.contentEditable=’true’; document.designMode=’on’; void 0

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Best Practices: Working with JavaScript’s

Thursday, May 15th, 2008 By Nikhil

Include JavaScript’s at the Bottom of the HTML Document

If you do not have document.write ( or any dynamic generation of page contents using javascripts) to insert part of the page’s content in your scripts, move the script include statement to the bottom of the page, before the end of the BODY tag.
The HTTP/1.1 specification suggests that browsers download no more than two components in parallel per hostname. If you serve your images from multiple hostnames, you can get more than two downloads to occur in parallel. While a script is downloading, however, the browser won’t start any other downloads, even on different hostnames.
There are also ways to dynamically create SCRIPT nodes and load remote scripts after the page is loaded using AJAX .

Externalise you JavaScript’s

Using external JavaScript files will result in faster loading of pages because the JavaScript files are cached by the browser. Inline JavaScript’s’ in HTML documents get downloaded every time the HTML document is requested. This might actually reduce the number of HTTP requests made but it subsequently increases the size of the HTML document. External JavaScript’s are cached by the browser; the size of the HTML document is reduced without increasing the number of HTTP requests.
Please note that, if users on your site have multiple page views per session and many of your pages re-use the same scripts and stylesheets, there is a greater potential benefit from cached external files.

Pack Your Javascript Files

In case of JavaScripts , unlike CSS, the files could crunched using some standard algorithms that would give a reduced file size than simply removing spaces or tabs. An example of javascript packer can be found here

Get rid of any Duplicate Scripts

It is very unusual that entire scripts might be duplicated, but a review of the ten top U.S. web sites shows that two of them contain a duplicated script. Duplicate scripts but obviously reduces the performance by creating unnecessary HTTP requests and wasted JavaScript execution.
Also, in many instances, though the scripts names are different, there is a likelihood of duplicate scripts within the same page due to team size and number of scripts.

Minimize accessing DOM elements where possible

Accessing DOM elements with JavaScript is slow so in order to have a more responsive page, you should:
• Cache references to accessed elements
• Update nodes “offline” and then add them to the tree
• Avoid fixing layout with JavaScript

Separate Behavior from Content and Presentation

Just as we separate Presentation (CSS/XSLT) from Content (XHTML/XML), we should also separate Behavior (Javascript). This is called unobtrusive Javascript. Just as we link to external CSS files, we should link to external javascript files.

Instead of hard coding behavior into the content (e.g. onmouseover, onclick, etc.), behavior should be dynamically added to elements, classes, and unique elements (IDs) using the DOM. The foundational document, the content, should contain only valid XHTML/XML and no javascript.
Javascript should augment content by adding behavior. The content should remain useful and usable without javascript (or without full javascript support).

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