What are chrome extensions

Guys,

Lets dive into the chrome ocean today..lets see how to build a chrome extension easily.

Developing extensions for your favorite browser helps not only you, but also other programmers, who sooner or later will be in the same situation. If something is missing, you can build it yourself and with Chrome this is really easy.

Architecture:

architecture

Manifest

The entry point of your extension is the manifest.json file. It should contain a valid JSON object. For example:

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{
    "name": "BrowserActionExtension",
    "version": "0.0.1",
    "manifest_version": 2,
    "browser_action": {
        "default_title": "That's the tool tip",
        "default_popup": "popup.html"
    }
}

The required properties are name, version, and manifest_version. The version can be anywhere from one to four, dot-separated integers. It’s something which is used by Google’s autoupdate system. That’s how it knows when to update your extension. The value of the manifest_version should be the integer 2.

The manifest could contain other properties depending on what kind of extension you need, but I’ll describe only those which I find to be more interesting.

Background Pages

Every extension has an invisible background page which is run by the browser. There are two types – persistent background pages and event pages. The first one is active, all of the time. The second is active only when it is needed

Here is how you should describe it in the manifest:

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"background": {
    "scripts": ["background.js"],
    "persistent": false/true
}

As you may have guessed, if the persistent property is false then you are using event pages. Otherwise, you are working with a persistent background page.

Content Script

If you need access to the current page’s DOM, then you have to use a content script. The code is run within the context of the current web page, which means that it will be executed with every refresh. To add such a script, use the following syntax.

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"content_scripts": [
    {
        "matches": ["http://*/*", "https://*/*"],
        "js": ["content.js"]
    }
]

Keep in mind that the value of matches determines for which pages your script will be used. Read more about matches patterns here.

User Interface

There are several ways to build the UI of your extension. Here are the four most popular.

Browser Action

Most developers use the browser_action property to build their plugins. Once you set it, an icon representing your extension will be placed on the right side of the address bar. Users can then click the icon and open a pop-up which is actually HTML content controlled by you.

The manifest files should contain the following data:

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"browser_action": {
    "default_icon": {
        "19": "icons/19x19.png",
        "38": "icons/38x38.png"
    },
    "default_title": "That's the tool tip",
    "default_popup": "popup.html"
}

The default_title is a little tool tip which is shown when the user mouses over your icon. default_popup is actually the HTML file which is loaded inside the pop-up. There is also a badge which you can place over your icon. You can do that inside of your background script. For example:

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chrome.browserAction.setBadgeText({text: "yeah"});

Page Action

The page_action property is similar to the browser action, but the icon is shown inside the address bar.

For example, the RSS icon will be shown only if the current page contains a link to the RSS feed. If you need to see your icon all the time, it is good to use browser_action directly.

To add the page action, type the following code inside your manifest:

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"page_action": {
    "default_icon": {
        "19": "images/icon19.png",
        "38": "images/icon38.png"
    },
    "default_title": "Google Mail",
    "default_popup": "popup.html"
}

Unlike the browser action’s icon, the page action’s icon doesn’t have badges.

DeveloperTools

I use DeveloperTools a lot and it’s nice that Chrome offers a method for adding new tabs to these tools. The first thing you should do is add an HTML page which will be loaded when the panel is opened:

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"devtools_page": "devtools.html"

There’s no need to put any HTML inside the page, except for linking in a JavaScript file, which will create the tab:

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<script src="devtools.js"></script>;

And then include the following code inside the devtools.js file:

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chrome.devtools.panels.create(
    "TheNameOfYourExtension",
    "img/icon16.png",
    "index.html",
    function() {
    }
);

Now the above code will add a new tab with a name of TheNameOfYourExtension and once you click on it the browser will load index.html inside the DeveloperTools.

How to install your chrome extensions?

In your browser’s address bar, just type in:

Make sure that you check Developer mode and click the Load unpacked extension… button. Then simply select the folder from your hard disk which contains the extension’s files.

extensionspanel

For more in detail..pls click here

Sources:

https://developer.chrome.com/extensions/getstarted

http://www.lullabot.com/blog/article/creating-simple-chrome-extension

http://www.sitepoint.com/build-your-own-chrome-extension-a-google-documents-word-count-tool/

http://www.9lessons.info/2011/03/how-to-create-chrome-extension.html

http://css-tricks.com/colorpeek-part-2-building-first-chrome-extension/

http://markashleybell.com/building-a-simple-google-chrome-extension.html

http://code.tutsplus.com/tutorials/developing-google-chrome-extensions–net-33076

http://lifehacker.com/5857721/how-to-build-a-chrome-extension

http://tutorialzine.com/2010/06/making-first-chrome-extension/

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