[qwertyuiop924]

The idea is inherently flawed. depandancy installation should be done as needed by people who are conciously aware of what they are doing. A better solution would be integrating NPM into your editor, so that package installation is trivial, but still explicit. M-x install-from-npm-region, anyone?

  (defun install-from-npm-region (start end)
    (interactive "r")
    (call-process 
      (concat "npm install " 
              (shell-quote-argument 
                (filter-buffer-substring start end)))
      nil
      (get-buffer-create "*NPM Output*")))

That function MIGHT install random things through NPM if your mark is unset, but it is, at least, explicit. And the random thing in question is your last region, so it's far more likely that NPM will just throw its hands and shout "what the hell?" Than actually install anthing...

Also note that that code hasn't been tested. I wouldn't copy this into my .emacs just yet, if I were you. Run it by somebody who actually knows elisp, first.