Hello i am completely new to arcgis js so for understanding coding pattern and concept is their any good source of video tutorial available on internet ?

[AnupamSharma]

It will most helpful

[JoeBorgione]

Dr Google is your friend:

https://developers.arcgis.com/javascript/3/jshelp/intro_firstmap_amd.html

http://help.arcgis.com/en/webapi/javascript/arcgis../jstutorials/

https://www.google.com/search?q=arcgis+javascript+tutorial&rlz=1C1GCEA_enUS763US763&source=lnms&tbm=...

[LanceCole]

Anupam Sharma‌, 

ESRI has a many free videos at their E360 site. As Joe Borgione noted above, Google and YouTube will be your best friends as well.

[RobertBorchert]

https://www.esri.com/training/catalog/580fc1dea4a46d172b116049/basics-of-javascript-web-apps/