Smart completion for javascript

Question

I ve just started to use Emacs. What I want to get is a kind of smart completion for javasacript. Not meaning just auto-complete ( which completes words I used on previous line ).

For example, if I write document. or Math. it should show me all possible/available functions which are built-in.

I think there is some plugin called cedet, though I am not sure if it does this for Javascript. If it does support that, I couldn't make it yet. Here is what I get in my init.el :

(semantic-mode 1)
(require 'semantic/ia)
(require 'semantic/db)

(semantic-ia-show-doc 1)
(semantic-ia-show-summary 1)
(semantic-ia-describe-class 1)
(global-semantic-highlight-func-mode 1)
(global-semantic-idle-local-symbol-highlight-mode 1)

and this is all init.el file before cedet confs: http://paste.lisp.org/display/139255

Answer 1

One solution abo-abo mentioned in the comments was ternjs.

(abo-abo: if you post your response as a real reply, I'll delete this answer)

Answer 2

As of 2021, everybody (and their mom) use LSP.