Deleting a subdocument by Id in Mongo using node.js

I am using nodejs, express, mongo and coffeescript and I have a simple blog post with comments, and I would like to add the possibility to delete a specific comment at any given time. The schema looks like this:

Schema = mongoose.Schema

ArticleSchema = new Schema
  title:
    type: String
    trim: true
    required: true

  body:
    type: String
    required: true

  createdAt:
    type: Date
    default: Date.now

  comments: [
    body:
      type: String
      default : ''

    user:
      type: Schema.ObjectId
      ref: 'User'
      required: true

    createdAt:
      type: Date
      default: Date.now
  ]

Routes for the article are mapped like this:

 articles = require '../app/controllers/articles'
 app.get '/', articles.index
 app.get '/articles', articles.manage
 app.get '/articles/new', auth.requiresLogin, articles.new
 app.get '/articles/:articleId', articles.show
 app.get '/articles/:articleId/edit', auth.requiresLogin, articles.edit

 app.param 'articleId', articles.article

But how do I do something like this to be able to delete a comment?

  app.get '/articles/:articleId/comment/:commentId/delete', auth.requiresLogin, articles.edit

If you mean how you should implement removal of a comment: you first retrieve the article document using articleId, and then you can find and remove the sub-document:

// find article
...

// find the comment by id, and remove it:
article.comments.id(commentId).remove();

// since it's a sub-document of article, you need
// to save the article back to the database to
// 'finalize' the removal of the comment:
article.save(function(err) { ... });