Answers for "how to create interface in angular npm"

install angular cli

npm install -g @angular/cli
ng new my-dream-app
cd my-dream-app
ng serve

angular cli interface generate

ng generate interface <name> <type> [options]
ng g interface <name> <type> [options]

# <name>	The name of the interface.
# <type>	Adds a developer-defined type to the filename, in the format "name.type.ts".
# [options]
#	--lintFix=true|false	When true, applies lint fixes after generating the interface (Default: false)
#	--prefix=prefix			A prefix to apply to generated selectors
#	--project=project		The name of the project.

# e.g.
# ng generate interface Itest sometype		generates file name		itest.sometype.ts