I'm writing a simple server for Node.js and I'm using my own class called User which looks like:
function User(socket) {
this.socket = socket;
this.nickname = null;
/* ... just the typical source code like functions, variables and bugs ... */
this.write = function(object) {
this.socket.write(JSON.stringify(object));
}
};
and then later in the process I'm instantiating it a lot:
var server = net.createServer(function (socket) {
/* other bugs */
var user = new User(socket);
/* more bugs and bad practise */
});
Can I move my User class definition to another javascript file and "include" it somehow?
You can simply do this:
user.js
class User {
//...
}
module.exports = User // 👈 Export class
server.js
const User = require('./user.js')
let user = new User()
This is called CommonJS module.
ES Modules
Since Node.js version 14 it's possible to use ES Modules with CommonJS. Read more about it in the ESM documentation.
user.mjs (👈 extension is important)
export default class User {}
server.mjs
import User from './user.mjs'
let user = new User()
Using ES6, you can have user.js:
export default class User {
constructor() {
...
}
}
And then use it in server.js
const User = require('./user.js').default;
const user = new User();
Modify your class definition to read like this:
exports.User = function (socket) {
...
};
Then rename the file to user.js. Assuming it's in the root directory of your main script, you can include it like this:
var user = require('./user');
var someUser = new user.User();
That's the quick and dirty version. Read about CommonJS Modules if you'd like to learn more.
Another way in addition to the ones provided here for ES6
module.exports = class TEST{
constructor(size) {
this.map = new MAp();
this.size = size;
}
get(key) {
return this.map.get(key);
}
length() {
return this.map.size;
}
}
and include the same as
var TEST= require('./TEST');
var test = new TEST(1);
If you append this to user.js:
exports.User = User;
then in server.js you can do:
var userFile = require('./user.js');
var User = userFile.User;
http://nodejs.org/docs/v0.4.10/api/globals.html#require
Another way is:
global.User = User;
then this would be enough in server.js:
require('./user.js');
Related
I read this question and attempted to do the solution, however I am trying to pass my instance of io to an object constructor instead of a class. I originally attempted to do something like...
//index.js
const {CONNECTION, CREATE_ROOM} = require('./SignalTypes')
const app = require('express')()
const server = require('http').Server(app)
const io = require('socket.io')(server)
const Lobbies = require('./lobby')
let lobbies = new Lobbies(io)
io.of('/menu').on(CONNECTION, (socket) => {
console.log(`User connected to main menu`)
socket.on(CREATE_ROOM, () => {
const roomKey = lobbies.createLobby()
socket.emit(ROOM_CREATED, roomKey)
})
...
})
And my Lobbies file looks like...
//lobby.js
const shortid = require('shortid')
function Lobbies(io) {
this.io = io;
this.lobbies = {}
}
Lobbies.prototype.createLobby = () => {
let roomKey = shortid.generate()
//create namespace for new lobby
const lobbyNamespace = this.io.of(`/${roomKey}`) // issue
this.lobbies[roomKey] = new Lobby(roomKey, lobbyNamespace)
return roomKey
}
//Lobby object constructor defined later
...
module.exports = Lobbies
However I keep running into errors in which it says io is undefined at the line
//lobby.js
const lobbyNamespace = this.io.of(`/${roomKey}`)
//TypeError: Cannot read property 'of' of undefined
I was wondering if there's a way to pass my io object to my object constructor without having to change it into an ES6 class or something. Any suggestions?
You are losing this reference when using arrow function syntax. I don't know why do you want to use old, hard-to-read syntax, but if you want that instead of class you should do:
Lobbies.prototype.createLobby = function() {
let roomKey = shortid.generate()
//create namespace for new lobby
const lobbyNamespace = this.io.of(`/${roomKey}`) // issue
this.lobbies[roomKey] = new Lobby(roomKey, lobbyNamespace)
return roomKey
}
In the below code snippet, how can I use osList and featureList using typescript can you please help me with this. I need to know how to work with a list of elements in the page object model like submitName function.
import { Selector, t } from 'testcafe';
const label = Selector('label');
class Feature {
constructor (text) {
this.label = label.withText(text);
this.checkbox = this.label.find('input[type=checkbox]');
}
}
class OperatingSystem {
constructor (text) {
this.label = label.withText(text);
this.radioButton = this.label.find('input[type=radio]');
}
}
export default class Page {
constructor () {
this.nameInput = Selector('#developer-name');
this.triedTestCafeCheckbox = Selector('#tried-test-cafe');
this.populateButton = Selector('#populate');
this.submitButton = Selector('#submit-button');
this.results = Selector('.result-content');
this.commentsTextArea = Selector('#comments');
this.featureList = [
new Feature('Support for testing on remote devices'),
new Feature('Re-using existing JavaScript code for testing'),
new Feature('Running tests in background and/or in parallel in multiple browsers'),
new Feature('Easy embedding into a Continuous integration system'),
new Feature('Advanced traffic and markup analysis')
];
this.osList = [
new OperatingSystem('Windows'),
new OperatingSystem('MacOS'),
new OperatingSystem('Linux')
];
this.slider = {
handle: Selector('.ui-slider-handle'),
tick: Selector('.slider-value')
};
this.interfaceSelect = Selector('#preferred-interface');
this.interfaceSelectOption = this.interfaceSelect.find('option');
this.submitButton = Selector('#submit-button');
}
async submitName (name) {
await t
.typeText(this.nameInput, name)
.click(this.submitButton);
}
}
I can describe this to you based on the TestCafe's basic example. First, you need to change the page-model file extension to ts and create this file according to the TypeScript rules (for example, see my gist). Then, you can change the test file extension to ts and start test execution like you do it for any js tests, e. g. testcafe chrome test.ts.
I'm learning nodejs now and Im wondering how can I reference to the object created in a other file
for example:
I have a file with my class user.js which I'm exporting
module.exports = class Username {
constructor(name, lastProjects) {
this.current.name = name;
this.current.lastProjects = lastProjects;
}
};
name.handler.js I can not export it this to oder files
const Alexa = require('alexa-sdk');
const User = require('../models/user.model');
module.exports = Alexa.CreateStateHandler(StatesConst.NAME, {
'NewSession': function () {
this.emit('NewSession'); // Uses the handler in newSessionHandlers
},
'MyNameIsIntent': function() {
var user = new User.Username("Anna", ["project1", "project2"]);
this.emit(':ask', "Hi "+User.Username.name);
}
}
user.handler.js I tottaly dont know how can I write a reference to my new created object Username
const Alexa = require('alexa-sdk');
const User = require('../models/user.model');
module.exports = Alexa.CreateStateHandler(StatesConst.NEWSTATE, {
'NewSession': function () {
this.emit('NewSession'); // Uses the handler in newSessionHandlers
},
'MyUserIntent': function() {
this.emit(':ask', "My username is "+User.Username.name);
}
}
How can I reference to new user object in other files in my programm ? I want that everytime my user starts a program I will get a new user object and I could reference and change attributes in every other file. I would be very appreciate for a help :)
module.exports = Username;
const Alexa = require('alexa-sdk'); // ok?
const User = // in linux, to go 1 dir up is just '.'
console.log(require('../models/user.model'))
see if you get a message = '[Function: Username]'".
If not you will see a message telling you something. Maybe no found file.
Since you are exporting Username by assigning it to module.exports, you need to use it as new User in your handlers. For example, name.handler.js would become:
const Alexa = require('alexa-sdk');
const User = require('../models/user.model');
module.exports = Alexa.CreateStateHandler(StatesConst.NAME, {
'NewSession': function () {
this.emit('NewSession'); // Uses the handler in newSessionHandlers
},
'MyNameIsIntent': function() {
var user = new User("Anna", ["project1", "project2"]);
this.emit(':ask', "Hi "+user.name);
}
}
Note that in the this.emit line, you should use the instance of User, not the class itself. (so user instead of User).
Moreover, in your user.handler.js file, you don't instantiate any User. You will get a Cannot read property 'name' of undefined
Finally if your Username class is in user.js, your require statement should look like require('../models/user'), not require('../models/user-model')
I have multiple nightwatch tests with setup and teardown in every single test. I am trying to unify it into globalModule.js in before after(path set in globals_path in nightwatch.json).
//globalModule.js
before:function(test, callback){
// do something with test object
}
//sampletest.js
before: function(test){
..
},
'testing':function(test){
....
}
My problem is test context is not available in globalsModule.js. How do i get it there? Can someone let me know?
Test contex not available now. As said beatfactor, it will available soon.
While it not available try use local before first file, but it hack.
Also you can export all your file into one object and export it into nightwatch, but then you can use local before just in time.
For example:
var tests = {};
var befores = [];
var fs =require('fs');
var requireDir = require('require-dir');
var dirs = fs.readdirSync('build');
//if you have dirs that should exclude
var usefull = dirs.filter(function(item){
return !(item=='data')
});
usefull.forEach(function(item){
var dirObj = requireDir('../build/' + item);
for(key in dirObj){
if(dirObj.hasOwnProperty(key))
for(testMethod in dirObj[key])
if(dirObj[key].hasOwnProperty(testMethod))
if(testMethod == 'before')
befores.push(dirObj[key][testMethod]);
else
tests[testMethod] = dirObj[key][testMethod];
}
});
tests.before = function(browser){
//some global before actions here
//...
befores.forEach(function(item){
item.call(tests,browser);
});
};
module.exports = tests;
For more information https://github.com/beatfactor/nightwatch/issues/388
Edit: Removed higher-level ideas, included problem-specific and less-transferable code.
I implemented my DAL using DAO's. My application hooks in to various databases (mostly for legacy reasons). In order to facilitate efficient and intelligent usage of connections, I use a ConnectionBroker singleton to manage the various connections that may (or may not be) open. This ConnectionBroker is then injected into the DAO's where they can request control of a particular connection object, request new connections, ect.
From an inheritence POV, I'd like something like:
AbstractDbConnection
|-- MongoDbConnection
|-- MsSqlConnection
|-- CouchDbConnection
|-- ...
Where AbstractDbConnection defines an interface, and implements some shared event-based logic.
var EventEmitter = require('events').EventEmitter;
module.exports = function AbstractDbConnection(host, port, database, login, ...) {
// private
var state = StatesEnum.Closed; // StatesEnum = {Open: 0, Closed: 1, ..}; Object.freeze(StatesEnum);
// api that must be overwritten
this.connect = function connect() {throw new ...}
this.disconnect = function disconnect() {throw new ...}
... <more>
this.getState = function() { return state; }
}
AbstractDbConnection.prototype.__proto__ = EventEmitter.prototype;
And then I implement the interface using driver-specific code:
var mssqldriver = require('mssqldriver'), //fictitious driver
AbstractDbConnection = require(__dirname + '/blah/AbstractDbConnection');
module.exports = function MsSqlConnection(host, port, database, login, ...) {
var me = this;
// implement using driver
this.connect = function connect() {...}
this.disconnect = function disconnect() {...}
... <more>
driverSpecificConnection.on('driverSpecificOpenEvent', function() {
me.emit('open'); // relay driver-specific events into common events
state = StatesEnum.Open; // how ??
}
...
}
MsSqlConnection.prototype.__proto__ = new AbstractDbConnection();
But clearly I want to protect the state property from changing inadvertently.
Just listen for the open event in the "abstract" constructor!
var EventEmitter = require('events').EventEmitter;
module.exports = AbstractDbConnection;
var StatesEnum = module.exports.StatesEnum = Object.freeze({
Open: 0, Closed: 1, …
});
function AbstractDbConnection(host, port, database, login, …) {
// private
var state = StatesEnum.Closed;
EventEmitter.call(this);
this.getState = function() { return state; }
this.on('open', function(e) {
state = StatesEnum.Open;
});
}
AbstractDbConnection.prototype = Object.create(EventEmitter.prototype);
// api that must be overwritten
AbstractDbConnection.prototype.connect = function connect() {throw new …};
AbstractDbConnection.prototype.disconnect = function disconnect() {throw new …};
var Mssqldriver = require('mssqldriver'), //fictitious driver
AbstractDbConnection = require(__dirname + '/blah/AbstractDbConnection');
module.exports = MsSqlConnection;
function MsSqlConnection(host, port, database, login, …) {
AbstractDbConnection.call(this);
this.driver = new Mssqldriver(…);
this.driver.on('driverSpecificOpenEvent', this.emit.bind(this, 'open'));
…
}
MsSqlConnection.prototype = Object.create(AbstractDbConnection.prototype);
MsSqlConnection.prototype.connect = function connect() {…};
MsSqlConnection.prototype.disconnect = function disconnect() {…};
You can use the module pattern to do this.
var transport_module = function() {
var mileage = 0; // private
return {
transport : function(distance) {
mileage += distance;
}
};
}
//use it
var car = transport_module(),
boat = transport_module(),
motorcycle = transport_module();
car.transport(10);
boat.transport(5);
motorcycle.transport(20);
The variable mileage is not visible to any other javascript code. Like a private java/C++ class variable. However, I would think about whether you need this kind of protection. I use modules a lot but not for small objects like class instances in java/C++.