title: How Nodejs insert a string to the n-th line of file easily?
body: <p>I googled around and checked a few npm (e.g. Lazy), but still couldn't find a good pattern to insert a string to n-th number of line of a file. </p>
  
  <p>Being a newbie to Nodejs, I suppose this could be done easily as in other languages, e.g. PHP / Ruby. </p>
  
  <p>Thanks for your solution in advance.</p>