Develop Reference

Node JS [Object Map] while writing object to file

I read many posts on stackoverflow and other tutorial sites for writing object/JSON to a file, but none of the solutions worked for me.
1) Code:
let messages = await fetchMessages()
console.log(messages) // Prints an object
fs.writeFileSync('./msgdata.json', messages , 'utf-8');
2) Also tried,
fs.writeFileSync('./msgdata.json', JSON.stringify(messages) , 'utf-8');
3) Also tried,
fs.writeFile(), but get same output as above.
msgdata.json: (For 1)
[object Map]
msgdata.json: (For 2 & 3)
{}
Can someone please point out what could be causing this?
## Output of console.log(messages) ##
OUTPUT contains 10 more such objects having different id's:
channel:
TextChannel {
type: 'text',
id: '424825532274253312',
name: 'request',
position: 69,
parentID: '397363224286473987',
permissionOverwrites: [Object],
topic: null,
nsfw: false,
lastMessageID: '427143105410760704',
guild: [Object],
messages: [Object],
_typing: Map {} },
id: '427142596817846272',
type: 'DEFAULT',
content: '**Select your emoji:** __***Group 9:***__',
author:
ClientUser {
id: '407083773537350272',
username: 'Bot',
discriminator: '9256',
avatar: '9c374e719ba2ab4e69fd577005b635bf',
bot: true,
lastMessageID: null,
lastMessage: null,
verified: true,
email: null,
localPresence: {},
_typing: Map {},
friends: Collection {},
blocked: Collection {},
notes: Collection {},
premium: null,
mfaEnabled: false,
mobile: null,
settings: [Object],
guildSettings: Collection {} },
member:
GuildMember {
guild: [Object],
user: [Object],
_roles: [Array],
serverDeaf: false,
serverMute: false,
selfMute: undefined,
selfDeaf: undefined,
voiceSessionID: undefined,
voiceChannelID: undefined,
speaking: false,
nickname: null,
joinedTimestamp: 1517127343434,
lastMessageID: null,
lastMessage: null },
pinned: false,
tts: false,
nonce: undefined,
system: false,
embeds: [],
attachments: Collection {},
createdTimestamp: 1521909131007,
editedTimestamp: null,
reactions:
Collection {
'taillow:417281639777959940' => [Object],
'shroomish:417281639899463680' => [Object],
'sableye:417281640197521419' => [Object],
'ralts:417281642735075329' => [Object],
'sentret:417281644001624076' => [Object],
'shuppet:417281644291162132' => [Object],
'torchic:417281647210397706' => [Object],
'snubbull:417281647692480522' => [Object],
'sunkern:417281647763783681' => [Object],
'slowpoke:417281648653107200' => [Object],
'teddiursa:417281649537974273' => [Object],
'sneasel:417281649613471747' => [Object],
'snorunt:417281649819123712' => [Object],
'surskit:417281650163056640' => [Object],
'qwilfish:417281654629859348' => [Object],
'shelgon:417281654730522624' => [Object] },
mentions:
MessageMentions {
everyone: false,
users: Collection {},
roles: Collection {},
_content: '**Select your emoji:** __***Group
9:***__',
_client: [Object],
_guild: [Object],
_members: null,
_channels: null },
webhookID: null,
hit: null,
_edits: [] },

This is because the object returned is a Map object (MDN). When you JSON.strigify a Map object, it always returns {}. There are two ways to get readable JSON that stores your map. The first is to loop over all the entries and create a JSON (taking in consideration the keys and values). That should be simple to achieve.
Another way is to create an array from the Map and then stringify it.
fs.writeFileSync('./msgdata.json', JSON.stringify([...myObject]) , 'utf-8');

You can define Map.prototype.toJSON which works, but it isn't standard and is discouraged. It is automatically called by JSON.stringify if it finds it.
Map.prototype.toJSON = function() {return [...this];};
console.log(JSON.stringify(messages));
A better way is to define your own replacer function (and reviver function too if you need to reconstruct map from JSON). Here I also wrap the map representing array in a special object to tell maps and ordinary arrays apart in JSON:
function replacer (key, value) {
if (value instanceof Map) {
return {
_type: "map",
map: [...value],
}
} else return value;
}
function reviver (key, value) {
if (value._type == "map") return new Map(value.map);
else return value;
}
let str = JSON.stringify(messages, replacer);
let msg = JSON.parse(str, reviver);
The error you are getting about circular structure means that some objects/arrays there contain references to itself. When you store messages you don't need to store all the information related to the channels etc and instead only store ids. So that means extending replacer for TextChannels, ClientUsers, GuildMembers etc:
if (value instanceof TextChannel) {
return {
_type: "TextChannel",
id: value.id,
};
}

var util = require('util');
fs.writeFileSync('./data.json', util.inspect(obj) , 'utf-8');
Ref. Write objects into file with Node.js

Getting the same Object back when using the array.filter with a valid condition

I am trying to get the value of the 'text' key in a Json object that I get from a GET request to twitter via the twit library.
Im trying to use the filter function on the array because i wanna do functional programming.
I can use the json object inside a callback function on the T.get function:
const gotData = function(err, data, response) {
console.log(data)
}
T.get('search/tweets', params , gotData)
Then I want to filter only the value on the text key on each of the statuses, which is an array of objects
So i tried this:
let results = data.statuses.filter(
function(result){ return result.hasOwnProperty('text')
})
But I get back the same data.statuses back... ?
I want to get only the value of the text keys on the objects, what im I doing wrong ?
this is my whole code:
const Twit = require('twit')
const config = require('./config')
const T = new Twit(config)
let params = { q: 'drum', count: 2 }
const gotData = function(err, data, response) {
let results = data.statuses.filter(function(result){ return result.hasOwnProperty('text')})
console.log(results)
}
T.get('search/tweets', params , gotData)
And this a sample of the Json response i get, which corresponds to the data on the gotData function:
{ statuses:
[ { created_at: 'Sun May 07 11:35:16 +0000 2017',
id: 861182642888343600,
id_str: '861182642888343552',
text: '#was_going \nEvery hunk bore seven drums,\nEvery drum owned seven drums…',
truncated: false,
entities: [Object],
metadata: [Object],
source: 'Cheap Bots, Done Quick!',
in_reply_to_status_id: 861181362954489900,
in_reply_to_status_id_str: '861181362954489856',
in_reply_to_user_id: 795028044758949900,
in_reply_to_user_id_str: '795028044758949888',
in_reply_to_screen_name: 'was_going',
user: [Object],
geo: null,
coordinates: null,
place: null,
contributors: null,
is_quote_status: false,
retweet_count: 0,
favorite_count: 0,
favorited: false,
retweeted: false,
lang: 'en' },
{ created_at: 'Sun May 07 11:35:09 +0000 2017',
id: 861182610596405200,
id_str: '861182610596405248',
text: 'Would you rather have Data storage or A pedal assembly for a bass drum or high hat cymbals?',
truncated: false,
entities: [Object],
metadata: [Object],
source: 'Cheap Bots, Done Quick!',
in_reply_to_status_id: null,
in_reply_to_status_id_str: null,
in_reply_to_user_id: null,
in_reply_to_user_id_str: null,
in_reply_to_screen_name: null,
user: [Object],
geo: null,
coordinates: null,
place: null,
contributors: null,
is_quote_status: false,
retweet_count: 0,
favorite_count: 0,
favorited: false,
retweeted: false,
lang: 'en' } ],
search_metadata:
{ completed_in: 0.034,
max_id: 861182642888343600,
max_id_str: '861182642888343552',
next_results: '?max_id=861182610596405247&q=drum&count=2&include_entities=1',
query: 'drum',
refresh_url: '?since_id=861182642888343552&q=drum&include_entities=1',
count: 2,
since_id: 0,
since_id_str: '0' } }

You just check if theres a text property. You might also want to map it to that property:
let results = data.statuses.filter(
result=>result.hasOwnProperty('text')
).map(result=>result.text);
http://jsbin.com/niwezocuhu/edit?console
Or if you take care on performance ( O(n) instead of O(n+n*r)):
let results= data.statuses.reduce((arr,result)=>(result.text&&arr.push(result.text)&&false)||arr,[]);

Node JS - pull VAR out of array

I trying to scrape data off a website. What is returned to me is an array that looks like.
var $ = cheerio.load(body)
returns:
{ [Function]
fn:
{ constructor: [Circular],
_originalRoot:
{ type: 'root',
name: 'root',
attribs: {},
children: [Object],
next: null,
prev: null,
parent: null } },
load: [Function],
html: [Function],
xml: [Function],
text: [Function],
parseHTML: [Function],
root: [Function],
contains: [Function],
The child object is what I'm after so...
var obj = $.root()[0]
returns:
{ type: 'root',
name: 'root',
attribs: {},
children:
[ { data: 'var usdata_real = { // All_data node opens\n\n\tATL: { // Country tag opens\n\t\tid: "ATL",\n\t\t\tdata: { // Data node begins\n\t\t\tq1_1980: 169.304888373489,\n\t\t\tq2_1980: 164.585093140904,\n\t\t\tq3_1980: 166.167521028595,\n\t\t\tq4_1980: 163.
....
I want the 'data' in this array.
obj = obj['children'][0]['data']
returns:
var usdata_real = { // All_data node opens
ATL: { // Country tag opens
id: "ATL",
data: { // Data node begins
q1_1980: 169.304888373489,
q2_1980: 164.585093140904,
q3_1980: 166.167521028595,
q4_1980: 163.040844286677,
q1_1981: 163.31019903107,
q2_1981: 162.449966027231,
q3_1981: 158.719442789479,
q4_1981: 162.744884934737,
.....
which is ALMOST perfect. Except it returns to me an array which is no bueno. I want to be able treat this as an object so i can do something like
obj['ATL']
and get they KEY/VALUE pairs.
So my question....
Is it possible to strip out the object in this array ('var usdata_real'). Because that is what I'm after.
Any tips would be greatly appreciated.
Thanks!

Javascript: how to loop and change key name?

How can I change key name but key its values?
For instance I have this json data that I have stored:
{ particles:
{ name: 'particles',
values: [ [Object], [Object], [Object], [Object], [Object] ] },
timestamps:
{ name: 'timestamps',
values: [ [Object], [Object], [Object], [Object], [Object] ] }
}
And I will loop this input and change the key:
{ particles: 'particle', timestamps: 'timestamp' }
Change particles to particle and timestamps to timestamp
My attemp:
for (var property in data) {
stored[data[property]] = stored[property].values;
stored[property].name = data[property];
}
I only managed to change the name's value inside the stored data but not the key name...
Any ideas?

Assign new property by getting old property value and then delete old property.
var data = {
particles: {
name: 'particles',
values: []
},
timestamps: {
name: 'timestamps',
values: []
}
}
var newK = {
particles: 'particle',
timestamps: 'timestamp'
};
// get all object keys and iterate over them
Object.keys(newK).forEach(function(ele) {
// assign object property based on old property value
data[newK[ele]] = data[ele];
// update name property
data[newK[ele]].name = newK[ele];
// delete old object property
delete data[ele];
})
console.log(data);

You can achieve it by iterating the data and create the new keys and delete the old ones.
E.g.
var data = {
particles: {
name: 'particles',
values: [ [Object], [Object], [Object], [Object], [Object] ]
},
timestamps: {
name: 'timestamps',
values: [ [Object], [Object], [Object], [Object], [Object] ]
}
};
var res = { particles: 'particle', timestamps: 'timestamp' };
for (var k in res) {
var newValue = res[k];
data[newValue] = data[k];
data[newValue].name = newValue;
delete data[k];
}

You first have to remove the key using the delete statement after that you can add the new property using the Static method of the Object class using the defineProperty method. Here it is sample code.
var data={ particles: 'particle', timestamps: 'timestamp' };
for(var k in data){
document.write(k+":"+data[k]+"<br/>");
}
if(data.hasOwnProperty("particles")){
value=data["particles"];
delete data["particles"];
Object.defineProperty(data,"particle",{
value: value,
writable: true,
enumerable: true,
configurable: true,
});
}
if(data.hasOwnProperty("timestamps")){
value=data["timestamps"];
delete data["timestamps"];
Object.defineProperty(data,"timestamp",{
value: value,
writable: true,
enumerable: true,
configurable: true,
});
}
document.write("<br/>new values <br/>");
for(var k in data){
document.write(k+":"+data[k]+"<br/>");
}
Happy Coding!!!
:)

You can convert your Object to a String using JSON.stringify, then replace any occurrences of particles or timestamps (str.replace(/particles/g, "particle")). Finally, convert your string back to an Object using JSON.parse(str).
NB: to make sure that you will not alter any other data but the keys:
str.replace(/{"particles":{"name":"particles"/g, '{"particle":{"name":"particle"')

How to loop over rows after .fetchAll Bookshelf js + knex js?

I have a MySQL Database which I need to query from node.js
I am using bookshelf and knex for this.
I want to get the contents of a table - I have defined a table in my model.js file. I am attempting the query like this:
//select * from completedSentences;
Model.CompletedSentences.fetchAll().then(function (resData) {
console.log(resData)
})
I would like to know how to loop over resData because it should be multiple rows.
The output of the console looks like this: I dont see a list of rows I can loop over.. What am i missing?
CollectionBase {
model:
{ [Function]
NotFoundError: [Function: ErrorCtor],
NoRowsUpdatedError: [Function: ErrorCtor],
NoRowsDeletedError: [Function: ErrorCtor] },
length: 1,
models:
[ ModelBase {
attributes: [Object],
_previousAttributes: [Object],
changed: {},
relations: {},
cid: 'c4',
id: 1 } ],
_byId:
{ '1':
ModelBase {
attributes: [Object],
_previousAttributes: [Object],
changed: {},
relations: {},
cid: 'c4',
id: 1 },
c4:
ModelBase {
attributes: [Object],
_previousAttributes: [Object],
changed: {},
relations: {},
cid: 'c4',
id: 1 } },
_knex: null,
_events: {},
_eventsCount: 0 }

I found the answer (the documentation is very cryptic, hope this helps others)
new Model.CompletedSentences().fetchAll().then(function (resData) {
_.each(resData.models, function (model) { //I am looping over models using underscore, you can use any loop
console.log(model.attributes)
})
})

Model.CompletedSentences.fetchAll().then(function (resData) {
console.log(resData.serialize())
})
output is in json format
http://bookshelfjs.org/#Model-instance-serialize

The Collection class has a set of lodash methods for this.
You can use collection.forEach this way:
new Model.CompletedSentences().fetchAll().then(function (completedSentences) {
completedSentences.forEach(function (model) {
console.log(model.attributes)
})
})
Check out the docs, there are many other useful methods for Collection.

If you dont want to use lodash, you can do this:
new Model.CompletedSentences().fetchAll().then(function (resData) {
resData.models.forEach( function (model) {
console.log(model.get('attribute');
console.log(model.related('sth').get('attribute');
})
})

simply just console with it attributes.
console.log(resData.attributes);
you will get results Objects vise.

Answer is simple, try this
console.log(resData.toJSON())