var prevPost = new Post();
console.log("#0 " + prevPost._id);
Object.assign(prevPost, post);
//prevPost._id = undefined;   // 새로운 아이디를 부여받기 위해 기존 _id 제거
console.log("#1 " + prevPost._id);
prevPost._id = undefined;
console.log("#2 " + prevPost._id);

prevPost.origin = post.key;
prevPost.key = shortid.generate(),

prevPost.save().then(output => {
    console.log("# prevPost is saved");
    console.log(output);
})


/* 오류메세지
received data = {
  "key": "BkKc1Ct-m",
  "title": "33",
  "writer": "mac.chrome",
  "content": "33ffvf",
  "date": 1529632023387,
  "isPrivate": false,
  "hasComment": true,
  "viewCnt": 2,
  "uuid": "HyIL0vO-7"
}
#0 5b2c55174b45901a42dec8ed
#1 5b2c4f91fa8a1712ad68cefc
#2 5b2c55174b45901a42dec8ee
## 1111
## 2222
{ ParallelSaveError: Can't save() the same doc multiple times in parallel. Document: 5b2c55174b45901a42dec8ee
    at ParallelSaveError.MongooseError [as constructor] (/Users/songmingu/Documents/project/talkplace/node_modules/mongoose/lib/error/index.js:12:11)
    at new ParallelSaveError (/Users/songmingu/Documents/project/talkplace/node_modules/mongoose/lib/error/parallelSave.js:18:17)
    at model.Model.save (/Users/songmingu/Documents/project/talkplace/node_modules/mongoose/lib/model.js:337:23)
    at Post.findOne.then.post (/Users/songmingu/Documents/project/talkplace/server/postRouter.js:68:22)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:188:7)
  message: 'Can\'t save() the same doc multiple times in parallel. Document: 5b2c55174b45901a42dec8ee',
  name: 'ParallelSaveError' }

*/



console.log("#0 " + JSON.stringify(post, null, 2));
let tmp = Object.assign({}, post);
tmp._id = undefined;
console.log("#1 " + JSON.stringify(tmp, null, 2));
var prevPost = new Post();
console.log("#2 " + JSON.stringify(prevPost, null, 2));
Object.assign(prevPost, tmp);
console.log("#3 " + JSON.stringify(prevPost, null, 2));

/*
received data = {
  "key": "BkKc1Ct-m",
  "title": "33",
  "writer": "mac.chrome",
  "content": "33ffvf",
  "date": 1529632436198,
  "isPrivate": false,
  "hasComment": true,
  "viewCnt": 2,
  "uuid": "HyIL0vO-7"
}
#0 {
  "_id": "5b2c4f91fa8a1712ad68cefc",
  "key": "BkKc1Ct-m",
  "title": "33",
  "writer": "mac.chrome",
  "content": "66",
  "date": 1529631000544,
  "isPrivate": false,
  "hasComment": true,
  "uuid": "HyIL0vO-7",
  "commentCnt": 0,
  "__v": 0,
  "viewCnt": 2,
  "origin": "BkKc1Ct-m"
}
#1 {
  "$__": {
    "strictMode": true,
    "selected": {},
    "getters": {},
    "_id": "5b2c4f91fa8a1712ad68cefc",
    "wasPopulated": false,
    "activePaths": {
      "paths": {
        "_id": "init",
        "key": "init",
        "title": "init",
        "writer": "init",
        "content": "init",
        "date": "init",
        "isPrivate": "init",
        "hasComment": "init",
        "uuid": "init",
        "commentCnt": "init",
        "__v": "init",
        "viewCnt": "init",
        "origin": "init"
      },
      "states": {
        "ignore": {},
        "default": {},
        "init": {
          "_id": true,
          "key": true,
          "title": true,
          "writer": true,
          "content": true,
          "date": true,
          "isPrivate": true,
          "hasComment": true,
          "uuid": true,
          "commentCnt": true,
          "__v": true,
          "viewCnt": true,
          "origin": true
        },
        "modify": {},
        "require": {}
      },
      "stateNames": [
        "require",
        "modify",
        "init",
        "default",
        "ignore"
      ]
    },
    "pathsToScopes": {},
    "emitter": {
      "domain": null,
      "_events": {},
      "_eventsCount": 0,
      "_maxListeners": 0
    },
    "$options": {
      "skipId": true,
      "isNew": false,
      "skipDefaults": {
        "_id": true,
        "key": true,
        "title": true,
        "writer": true,
        "content": true,
        "date": true,
        "isPrivate": true,
        "hasComment": true,
        "uuid": true,
        "commentCnt": true,
        "__v": true,
        "viewCnt": true,
        "origin": true
      }
    }
  },
  "isNew": false,
  "_doc": {
    "_id": "5b2c4f91fa8a1712ad68cefc",
    "key": "BkKc1Ct-m",
    "title": "33",
    "writer": "mac.chrome",
    "content": "66",
    "date": 1529631000544,
    "isPrivate": false,
    "hasComment": true,
    "uuid": "HyIL0vO-7",
    "commentCnt": 0,
    "__v": 0,
    "viewCnt": 2,
    "origin": "BkKc1Ct-m"
  },
  "$init": true
}
#2 {
  "_id": "5b2c56b47e127a1b2e8f6acb"
}
#3 {
  "_id": "5b2c56b47e127a1b2e8f6acc",
  "key": "BkKc1Ct-m",
  "title": "33",
  "writer": "mac.chrome",
  "content": "66",
  "date": 1529631000544,
  "isPrivate": false,
  "hasComment": true,
  "uuid": "HyIL0vO-7",
  "commentCnt": 0,
  "__v": 0,
  "viewCnt": 2,
  "origin": "BkKc1Ct-m"
}
## 1111
## 2222
{ ParallelSaveError: Can't save() the same doc multiple times in parallel. Document: 5b2c56b47e127a1b2e8f6acc
    at ParallelSaveError.MongooseError [as constructor] (/Users/songmingu/Documents/project/talkplace/node_modules/mongoose/lib/error/index.js:12:11)
    at new ParallelSaveError (/Users/songmingu/Documents/project/talkplace/node_modules/mongoose/lib/error/parallelSave.js:18:17)
    at model.Model.save (/Users/songmingu/Documents/project/talkplace/node_modules/mongoose/lib/model.js:337:23)
    at Post.findOne.then.post (/Users/songmingu/Documents/project/talkplace/server/postRouter.js:69:22)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:188:7)
  message: 'Can\'t save() the same doc multiple times in parallel. Document: 5b2c56b47e127a1b2e8f6acc',
  name: 'ParallelSaveError' }
*/