mel.js

## mel.js
class BlockOfComments {
  var id; // just in case
  var numberOfComments;
  var comments[]; //array of Comment instances

  var addComment = function(text, ownerID, parent){
    var comment = new Comment(text, ownerID, parent);
    var indexOfComment = this.comments.indexOf(comment);
    if (index != -1) {
      alert("comment already exist");
    } else {
      this.comments.push(comment);
    }
    this.numberOfComments = comments.length;
  }

  var deleteCommentById = function(commentID) {

    function findCommentByID(comment){
      return comment.id === commentID;
    }

    var indexToDelete = this.comments.findIndex(findCommentByID);
    if(indexToDelete != -1) {
    	this.comments.splice(indexToDelete, 1);
    }
    this.numberOfComments = comments.length;
  }
}

class Comment {
  var id;
  var parentCommentID = null; //may be null (optional type)
  var ownerID; //userID
  var text;
  var numberOfLikes;
  var likes[]; //array of IDs who like this comment

  construcor(text, ownerID, parentID) {
    this.text = text;
    this.ownerID = ownerID;
    if parentID {
      this.parentID = parentID;
    }
  }

  var like = function(userID){
    var indexOfUserID = this.likes.indexOf(userID)
    if (index != -1) { // if user already like this then delete like from arr
      this.likes.splice(index, 1)
    } else {  // if user not liked before then add like to arr
      this.likes.push(userID);
    }
    this.numberOfLikes = this.likes.length;
  }
}