HI Nagaraju,
Everything you could possibly want to do with the javascript client is documented in the client api docs.
https://apidocs.mendix.com/7/client/mx.data.html#.action
This one can show you how to call a microflow.
Also take a look at the widget boilerplate on Github:
https://github.com/mendix/AppStoreWidgetBoilerplate
Most of the time someone in the community has already built a lot of the functionality your looking for. So take a look on the appstore there might be a widget that does 90% -100% what you want. The beauty of the widgets is they are all open sourced and easily customisable.
Simon