Develop Reference

How to send JSON inside of class syntax to an API?

Let's say I have a normal mjs file and an API such as this:
// Storage.mjs
class Storage {
constructor(name, age) {
this.name = name;
this.age = age;
this.json = JSON.stringify(this);
}
}
var store = new Storage('eMart', 2);
// server.js
var express = require('express'),
fs = require('fs'),
data = fs.readFileSync('website/js/storage.mjs'),
convert = JSON.parse(data);
var app = express(),
server = app.listen(3000, initialize);
console.log(convert);
function initialize() {
console.log("Local Host Initialized.");
}
app.use(express.static('website'));
My goal is to send the JSON data to API which is inside of class syntax, but every time Node keeps throwing undefined and an error like this picture;
Most of people's question was sending data from API to specific js file which was totally opposite of my case. It was hard to find solution from there.
Are there any proper ways to pass JSON data to API?

I suppose this is what you want?
// assume this is loaded with fs.readFileSync
const mjs = `
class Storage {
constructor(name, age) {
this.name = name;
this.age = age;
this.json = JSON.stringify(this);
}
}
var store = new Storage('eMart', 2); // I assume you missed the quote here
`;
eval(mjs); // You can't just convert an js file into a JSON, you have to eval it first(not safe, use it with caution)
let result = JSON.parse(store.json); // Since the file outputs a variable called "store" and it has a "json" property
console.log(result);
The server.js snippet
// server.js
var express = require('express'),
fs = require('fs'),
data = fs.readFileSync('website/js/storage.mjs');
(0, eval)(data); // indirect eval
var convert = JSON.parse(store.json);
var app = express(),
server = app.listen(3000, initialize);
console.log(convert);
function initialize() {
console.log("Local Host Initialized.");
}
app.use(express.static('website'));

How to pass variable to other modules with NodeJS?

I want to pass my logServiceClient object to all other modules included in server.js file. When I run below code it prints empty object;
logServiceClient{}
Is there any way to pass logServiceClient to all other included modules?
server.js file;
....
const logger = new Logger({
level: new CLevel('warn'),
ordered
})
var logServiceClient = require('./app/logServiceClient')(logger)
var userHandler = require('./app/userHandler')(logServiceClient)
userHandler file;
module.exports = function(logServiceClient){
console.log('logServiceClient' + JSON.stringify(logServiceClient))
}

There a many ways to inject without pulling in the logger from your other modules.
Use a factory to indirectly create and initialize your objects/modules
function factoryCreateModule() {
var client = require('client')
client.$logger = require('logger')
}
function factoryRequireModule(module) {
var client = require(module)
client.$logger = require('logger')
}
var client = factoryCreateModule()
client.logger.log('hello')
var client2 = factoryRequireModule('client')
client2.logger.log('hello')
Add your logger to all objects using prototype
Of course you can narrow down the target object...
var logger = {
log(message) {
console.log(message)
},
warn(message) {
console.log('!!! ' + message)
}
}
Object.prototype.$logger = logger
var x = 12;
x.$logger.log('I am a number')
var str = "Hello"
str.$logger.warn('WARNING FROM STRING')
Make your logger global
global is the 'window' in the module system.
// just for snippit to run
window.global = {}
var logger = {
log(message) {
console.log(message)
}
}
// main module
global.$logger = logger
// client module
global.$logger.log('hello world')
Pass the logger into the constructor or init method
var logger = require('logger')
var client = require('client')(logger)
var client2 = require('client2')({logger})
var client3 = require('client3')
client3.init(logger)

// file1.js
var foo = "bar";
exports.foo = foo;
//file2.js
var myModule = require('./file1');
var foo = myModule.foo;

How to export functions from modules in node.js

I am using node.js (v4.2.2) with express (4.13.1). I am trying to import my custom module functions to another module. Application is created with express, and only thing added to app.js is require for my route var tests = require('./routes/tests'); and app.use for that route app.use('/tests', tests);
My two custom files (modules) are (path is relative to project root):
./model/test.js
./routes/tests.js
Here is ./model/test.js:
var id;
var testNumber1;
var testNumber2;
function Test(id, testNumber1, testNumber2) {
this.id = id;
this.testNumber1 = testNumber1;
this.testNumber2 = testNumber2;
};
exports.reset = function() {
this.testNumber1 = 0;
this.testNumber2 = 0;
};
module.exports = Test;
And here is ./routes/tests.js:
var express = require('express');
var Red = require('../model/test.js');
var router = express.Router();
/*create new test :id*/
router.post('/:id', function(req, res, next) {
var myNewTest = new Red(req.params.id, 0, 0)
myNewTest.testNumber2 += 1;
myNewTest.reset();
res.send('id: ' + myNewTest.id +
' testNumber2: ' + myNewTest.testNumber2);
});
module.exports = router;
When I try to execute curl -X POST http://localhost:3000/tests/1 i get error TypeError: myNewTest.reset is not a function. I am having trouble understanding how to export functions correctly. If I understand this api reference correctly, to expose constructor of module, i have to use module.exports = Test;, but that doesn't expose reset function. So, to expose it I have declared it like exports.reset = function() {...}, but obviously, that doesn't work, at least not in my case.
Through some other answers I have also seen function being declared normally function reset() {...}, and exposed like exports.reset = reset;, which gives me the same error.
How do I expose reset function properly?

You should add it to the prototype, at the moment it's just a static method in your module, not attached to the Test constructor.
function Test(id, testNumber1, testNumber2) {
this.id = id;
this.testNumber1 = testNumber1;
this.testNumber2 = testNumber2;
};
Test.prototype.reset = function() {
this.testNumber1 = 0;
this.testNumber2 = 0;
};
module.exports = Test;

Node.JS undefined is not a function on required module

I'm trying to use a class that I created called user.js. The code for this user is:
function User(){};
User.prototype.addUser = function(){
//Do stuff
return 0;
};
module.exports = User;
I'm including it in my index.js route file, which looks like this:
var config = require('../lib/config');
var db = require('../lib/db');
var User = require('../lib/user');
var express = require('express');
var router = express.Router();
var bodyParser = require('body-parser');
/* GET home page. */
router.get('/', function(req, res, next) {
res.render('index', { title: 'Express' });
});
/* GET create user. */
router.get('/newuser', function(req, res, next) {
*****var newuser = User.addUser();*****
res.render('index', {
user: newuser
});
});
module.exports = router;
However, when I visit localhost/newuser, I get the following error: TypeError: undefined is not a function. This error is being thrown in index.js on the line I marked with 5 asterisks above.

You are defining a constructor named User() and exporting it. But, then when you require('../lib/user'), you get the constructor function, but you never construct a new object with it so you don't actually have an object of type User, you just have the constructor and thus there is no method addUser() on the constructor.
Instead of this:
var User = require('../lib/user');
you can call the constructor function like this:
var u = require('../lib/user');
var User = new u();
Or, if you never need to make another one, you can do it all in one line:
var User = new (require('../lib/user'))();

Another way would be to change your User.js class to return something on these lines...
function User(){};
User.prototype.addUser = function(){
//Do stuff
return 0;
};
module.exports = new User();

include external .js file in node.js app

I have an app.js node application. As this file is starting to grow, I would like to move some part of the code in some other files that I would "require" or "include" in the app.js file.
I'm trying things like:
// Declare application
var app = require('express').createServer();
// Declare usefull stuff for DB purposes
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;
// THE FOLLOWING REQUIRE DOES NOT WORK
require('./models/car.js');
in car.js:
// Define Car model
CarSchema = new Schema({
brand : String,
type : String
});
mongoose.model('Car', CarSchema);
I got the error:
ReferenceError: Schema is not defined
I'm just looking to have the content of car.js loaded (instead of having everything in the same app.js file) Is there a particuliar way to do this in node.js ?

To place an emphasis on what everyone else has been saying var foo in top level does not create a global variable. If you want a global variable then write global.foo. but we all know globals are evil.
If you are someone who uses globals like that in a node.js project I was on I would refactor them away for as there are just so few use cases for this (There are a few exceptions but this isn't one).
// Declare application
var app = require('express').createServer();
// Declare usefull stuff for DB purposes
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId;
require('./models/car.js').make(Schema, mongoose);
in car.js
function make(Schema, mongoose) {
// Define Car model
CarSchema = new Schema({
brand : String,
type : String
});
mongoose.model('Car', CarSchema);
}
module.exports.make = make;

The correct answer is usually to use require, but in a few cases it's not possible.
The following code will do the trick, but use it with care:
var fs = require('fs');
var vm = require('vm');
var includeInThisContext = function(path) {
var code = fs.readFileSync(path);
vm.runInThisContext(code, path);
}.bind(this);
includeInThisContext(__dirname+"/models/car.js");

Short answer:
// lib.js
module.exports.your_function = function () {
// Something...
};
// app.js
require('./lib.js').your_function();

you can put
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
at the top of your car.js file for it to work, or you can do what Raynos said to do.

If you just want to test a library from the command line, you could do:
cat somelibrary.js mytestfile.js | node

This approach works for me in Node.js, Is there any problem with this one?
File 'include.js':
fs = require('fs');
File 'main.js':
require('./include.js');
fs.readFile('./file.json', function (err, data) {
if (err) {
console.log('ERROR: file.json not found...')
} else {
contents = JSON.parse(data)
};
})