Javascript – > left side monitor

yarn “ERROR: There are no scenarios; must have at least one.

November 30, 2020November 30, 2020 by devmin

If you have this error when running yarn, chances are you have installed the wrong yarn package which come from cmdtest, let’s remove it and install the correct one using npm

sudo apt remove cmdtest
npm install -g yarn

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Mongoose save() not working/saving

October 15, 2020October 15, 2020 by devmin

If save() does not save the entity to mongodb database, probably there’s something wrong with the data itself like containing _id field

delete data._id; //clean up to ensure no _id field.
let user = new User(data);
user.save();

Also it is better to provide error handling so we can read what went wrong using the log.

let user = new User(data);
user.save(function (err) {
            if (err) {
                console.log(err);
            }
        });

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Javascript return object from one file to another file, include class javascript

October 13, 2020 by devmin

In Javascript, to include a class, constant or definition from one file to another we need to use exports. exports and module.exports are pointing to the same object, so sometimes you can see both styles.

class Employee {
  constructor(name, age, email) {
    this.name = name;
    this.age = age;
    this.email = email;
  }

  getStats() {
    return `
      Name: ${this.name}
      Age: ${this.age}
      Email: ${this.email}
    `;
  }
}

module.exports = Employee;

var Employee = require('../models/employee');

Employee employee = new Employee('Robin hood', 1000, '[email protected]');

var Employee = require('./models/employee');

Employee employee = new Employee('Robin hood', 1000, '[email protected]');

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Separate / Split express app.js into smaller files and put in different folders

October 13, 2020 by devmin

Imagine the original app.js is this long file, how to split app.js of express into smaller files is as following

var http = require('http'),
    path = require('path'),
    methods = require('methods'),
    express = require('express'),
    bodyParser = require('body-parser'),
    session = require('express-session'),
    cors = require('cors'),
    passport = require('passport'),
    errorhandler = require('errorhandler'),
    mongoose = require('mongoose');

var isProduction = process.env.NODE_ENV === 'production';

// Create global app object
var app = express();
var router = app.Router();

app.use(cors());

// Normal express config defaults
app.use(require('morgan')('dev'));
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());

app.use(require('method-override')());
app.use(express.static(__dirname + '/public'));

app.use(session({ secret: 'conduit', cookie: { maxAge: 60000 }, resave: false, saveUninitialized: false  }));

if (!isProduction) {
  app.use(errorhandler());
}

if(isProduction){
  mongoose.connect(process.env.MONGODB_URI);
} else {
  mongoose.connect('mongodb://localhost/conduit');
  mongoose.set('debug', true);
}

var passport = require('passport');
var LocalStrategy = require('passport-local').Strategy;
var mongoose = require('mongoose');
var User = mongoose.model('User');

passport.use(new LocalStrategy({
  usernameField: 'user[email]',
  passwordField: 'user[password]'
}, function(email, password, done) {
  User.findOne({email: email}).then(function(user){
    if(!user || !user.validPassword(password)){
      return done(null, false, {errors: {'email or password': 'is invalid'}});
    }

    return done(null, user);
  }).catch(done);
}));


router.get('/user', auth.required, function(req, res, next){
  User.findById(req.payload.id).then(function(user){
    if(!user){ return res.sendStatus(401); }

    return res.json({user: user.toAuthJSON()});
  }).catch(next);
});

router.put('/user', auth.required, function(req, res, next){
  User.findById(req.payload.id).then(function(user){
    if(!user){ return res.sendStatus(401); }

    // only update fields that were actually passed...
    if(typeof req.body.user.username !== 'undefined'){
      user.username = req.body.user.username;
    }
    if(typeof req.body.user.email !== 'undefined'){
      user.email = req.body.user.email;
    }
    if(typeof req.body.user.bio !== 'undefined'){
      user.bio = req.body.user.bio;
    }
    if(typeof req.body.user.image !== 'undefined'){
      user.image = req.body.user.image;
    }
    if(typeof req.body.user.password !== 'undefined'){
      user.setPassword(req.body.user.password);
    }

    return user.save().then(function(){
      return res.json({user: user.toAuthJSON()});
    });
  }).catch(next);
});

/// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

/// error handlers

// development error handler
// will print stacktrace
if (!isProduction) {
  app.use(function(err, req, res, next) {
    console.log(err.stack);

    res.status(err.status || 500);

    res.json({'errors': {
      message: err.message,
      error: err
    }});
  });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  res.json({'errors': {
    message: err.message,
    error: {}
  }});
});

// finally, let's start our server...
var server = app.listen( process.env.PORT || 3000, function(){
  console.log('Listening on port ' + server.address().port);
});

Split passport and routes

var http = require('http'),
    path = require('path'),
    methods = require('methods'),
    express = require('express'),
    bodyParser = require('body-parser'),
    session = require('express-session'),
    cors = require('cors'),
    passport = require('passport'),
    errorhandler = require('errorhandler'),
    mongoose = require('mongoose');

var isProduction = process.env.NODE_ENV === 'production';

// Create global app object
var app = express();

app.use(cors());

// Normal express config defaults
app.use(require('morgan')('dev'));
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());

app.use(require('method-override')());
app.use(express.static(__dirname + '/public'));

app.use(session({ secret: 'conduit', cookie: { maxAge: 60000 }, resave: false, saveUninitialized: false  }));

if (!isProduction) {
  app.use(errorhandler());
}

if(isProduction){
  mongoose.connect(process.env.MONGODB_URI);
} else {
  mongoose.connect('mongodb://localhost/conduit');
  mongoose.set('debug', true);
}

require('./config/passport');

app.use(require('./routes'));

/// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

/// error handlers

// development error handler
// will print stacktrace
if (!isProduction) {
  app.use(function(err, req, res, next) {
    console.log(err.stack);

    res.status(err.status || 500);

    res.json({'errors': {
      message: err.message,
      error: err
    }});
  });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  res.json({'errors': {
    message: err.message,
    error: {}
  }});
});

// finally, let's start our server...
var server = app.listen( process.env.PORT || 3000, function(){
  console.log('Listening on port ' + server.address().port);
});

var passport = require('passport');
var LocalStrategy = require('passport-local').Strategy;
var mongoose = require('mongoose');
var User = mongoose.model('User');

passport.use(new LocalStrategy({
  usernameField: 'user[email]',
  passwordField: 'user[password]'
}, function(email, password, done) {
  User.findOne({email: email}).then(function(user){
    if(!user || !user.validPassword(password)){
      return done(null, false, {errors: {'email or password': 'is invalid'}});
    }

    return done(null, user);
  }).catch(done);
}));

var mongoose = require('mongoose');
var router = require('express').Router();
var passport = require('passport');
var User = mongoose.model('User');
var auth = require('../auth');

router.get('/user', auth.required, function(req, res, next){
  User.findById(req.payload.id).then(function(user){
    if(!user){ return res.sendStatus(401); }

    return res.json({user: user.toAuthJSON()});
  }).catch(next);
});

router.put('/user', auth.required, function(req, res, next){
  User.findById(req.payload.id).then(function(user){
    if(!user){ return res.sendStatus(401); }

    // only update fields that were actually passed...
    if(typeof req.body.user.username !== 'undefined'){
      user.username = req.body.user.username;
    }
    if(typeof req.body.user.email !== 'undefined'){
      user.email = req.body.user.email;
    }
    if(typeof req.body.user.bio !== 'undefined'){
      user.bio = req.body.user.bio;
    }
    if(typeof req.body.user.image !== 'undefined'){
      user.image = req.body.user.image;
    }
    if(typeof req.body.user.password !== 'undefined'){
      user.setPassword(req.body.user.password);
    }

    return user.save().then(function(){
      return res.json({user: user.toAuthJSON()});
    });
  }).catch(next);
});

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Javascript MapReduce Foreach

October 11, 2020October 11, 2020 by devmin

let fruits = [
    {key: 0, name: 'Apple'},
    {key: 1, name: 'Banana'},
    {key: 2, name: 'Orange'},
    {key: 3, name: 'Grape'}
];

fruits.filter(function (fruit) {
    return fruit.key % 2 == 1; // 1 and 3
}).map(function (fruit) {
    return fruit.key + ':' + fruit.name;
}).forEach(function (fruit) {
    console.log(fruit);
});
----------
1:Banana
3:Grape

fruits.filter(function (fruit) {
    return fruit.key % 2 == 0; // 0 and 2
}).map(function (fruit) {
    return fruit.key + ':' + fruit.name;
}).forEach(function (fruit) {
    console.log(fruit);
});
----------
0:Apple
2:Orange

var total = fruits.filter(function (fruit) {
    return fruit.key % 2 == 1; // 1 and 3
}).map(function (fruit) {
    return fruit.key * 5; // 1 * 5, 3 * 5
}).reduce(function (acc, score) {
    return acc + score; //accumulate 1 * 5 + 3 * 5
}, 0);
console.log(total);
----------
20

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Loop thought object Javascript

October 11, 2020October 11, 2020 by devmin

const states = {
        "AL": "Alabama",
        "AK": "Alaska",
        "AS": "American Samoa",
        "AZ": "Arizona",
        "AR": "Arkansas",
        "CA": "California"
};
const entries = Object.entries(states);
for (const [abbr, name] of entries) {  
  console.log(`abbr: ${abbr}, name: ${name}`);
}

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List of USA states in Javascript

October 11, 2020October 11, 2020 by devmin

module.exports = Object.freeze({
    STATES: {
        "AL": "Alabama",
        "AK": "Alaska",
        "AS": "American Samoa",
        "AZ": "Arizona",
        "AR": "Arkansas",
        "CA": "California",
        "CO": "Colorado",
        "CT": "Connecticut",
        "DE": "Delaware",
        "DC": "District Of Columbia",
        "FM": "Federated States Of Micronesia",
        "FL": "Florida",
        "GA": "Georgia",
        "GU": "Guam",
        "HI": "Hawaii",
        "ID": "Idaho",
        "IL": "Illinois",
        "IN": "Indiana",
        "IA": "Iowa",
        "KS": "Kansas",
        "KY": "Kentucky",
        "LA": "Louisiana",
        "ME": "Maine",
        "MH": "Marshall Islands",
        "MD": "Maryland",
        "MA": "Massachusetts",
        "MI": "Michigan",
        "MN": "Minnesota",
        "MS": "Mississippi",
        "MO": "Missouri",
        "MT": "Montana",
        "NE": "Nebraska",
        "NV": "Nevada",
        "NH": "New Hampshire",
        "NJ": "New Jersey",
        "NM": "New Mexico",
        "NY": "New York",
        "NC": "North Carolina",
        "ND": "North Dakota",
        "MP": "Northern Mariana Islands",
        "OH": "Ohio",
        "OK": "Oklahoma",
        "OR": "Oregon",
        "PW": "Palau",
        "PA": "Pennsylvania",
        "PR": "Puerto Rico",
        "RI": "Rhode Island",
        "SC": "South Carolina",
        "SD": "South Dakota",
        "TN": "Tennessee",
        "TX": "Texas",
        "UT": "Utah",
        "VT": "Vermont",
        "VI": "Virgin Islands",
        "VA": "Virginia",
        "WA": "Washington",
        "WV": "West Virginia",
        "WI": "Wisconsin",
        "WY": "Wyoming"
    }
});

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