Need proper steps to work with XPCOM, XUL and Javascript to create Firefox Addons (Plugins/Extension)

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Firefox

Tried below steps, but I could not execute any XPCOM codes in my local machine.
It's throwing error like

Components are not recognized in Javascript.

Steps Followed:

1.Addon SDK installed
2.XUL Runner installed
3.Gecko installed

Then tried the XPCOM examples given in below links, but I got the above mentioned error.

1. https://developer.mozilla.org/en-US/docs/How_to_Build_an_XPCOM_Component_in_Javascript[^]

2. https://developer.mozilla.org/en-US/docs/Accessing_the_Windows_Registry_Using_XPCOM[^]

Please help me how to work with XPCOM and provide clear steps where we need start first.