Webstorm JavaScript External Libraries vs Project Directories -

in iis , therefore vs, there virtual directories allow simplified, virtual, relative referencing in script tags. handy. in webstorm can same effect project directories , marking project root resource root. if this, coding assistance in text editor.

webstorm has external libraries, point of these?
when have link cdn in script tag , want coding assistance? if have project directories, point of external libraries?

i've seen this answer , kind of different modes of referencing/inclusion, don't big picture. core reason external libraries vs project directories?

is when have link cdn in script tag , want coding assistance?

yes, common case - webstorm can't use online resources code assistance, needs have corresponding javascript files available locally. so, if don't pollute project folder these library files, can have them stored outside of project , set libraries.

what core reason external libraries vs project directories?

see above - external libraries allow storing library files in arbitrary location outside project folder , still code completion/highlighting/etc. please see answer refer to:

note libraries 'light-weight' compared .js files in project - treated read-only, have inspections turned off. plus, can assign documentation urls them, enabling external documentation library code. so, if have library files in project, might make sense add them libraries 

see this blog post