When i try to import such as like this in server.js:
import SalaryService from '/components/utils/SalaryService';
and then want to use it like this:
const salaryService = new SalaryService();
res.send(salaryService.getSalaries('test'));
However I get the following error message when I try start my dev server:
C:\projects\project\server.js:10
import SalaryService from '/components/utils/SalaryService';
^^^^^^
SyntaxError: Unexpected token import
How could I achieve this?
Nodejs doesn't support ES6 modules syntax
If you want to use ES6 modules syntax you can use babel to run your code
Depends on what module.exports in '/components/utils/SalaryService' is assigned. If it's an object with many functions (or nested objects), meaning the file SalaryService.js exports an object containing a property called 'SalaryService' you can use destructuring like so:
const { SalaryService } = require('/components/utils/SalaryService');
This is nice because you can pick a few properties from a large object cleanly:
const { SalaryService, SomeOtherProp } = require('/components/utils/SalaryService');
Otherwise if the module.exports is assigned the function or object you want directly:
const SalaryService = require('/components/utils/SalaryService');
Related
I have a query with the syntax in the require statement. Please refere the sample code below.
const nodemailer = require("nodemailer");
const {google} =require('googleapis');
const {OAuth2}=google.auth;
Some times , I see sample codes which use
const {<variable>} = require('moduleName')
Other times, I see like below
const <variable> = require('moduleName')
What is the difference between them?
Thanks in Advance.
Grateful to the Developers Community.
So, you use { } in this context when you want to do object destructuring to get a property from the exported object and create a module-level variable with that same name.
This:
const { google } = require('googleapis');
is a shortcut for this:
const __g = require('googleapis');
const google = __g.google;
So, within this context, you use the { google } only when you want the .google property from the imported module.
If you want the entire module handle such as this:
const nodemailer = require("nodemailer");
then, you don't use the { }. The only way to know which one you want for any given module is to consult the documentation for the module, the code for the module or examples of how to use the module. It depends entirely upon what the module exports and whether you want the top level export object or you want a property of that object.
It's important to realize that the { } used with require() is not special syntax associated with require(). This is normal object destructuring assignment, the same as if you did this:
// define some object
const x = { greeting: "hello" };
// use object destructuring assignment to create a new variable
// that contains the property of an existing object
const { greeting } = x;
console.log(greeting); // "hello
When you import the function with {}, it means you just import one function that available in the package. Maybe you have've seen:
const {googleApi, googleAir, googleWater} = require("googleapis")
But, when you not using {}, it means you import the whole package, just write:
const google = require("googleapis")
So, let say when you need googleApi in your code. You can call it:
google.googleApi
I'm trying to use cy.taks() to load certain datasets to mongo before a test is run. But I'm getting errors. I've got a module where I export 2 functions, one from dropping a collection, and the other to load an object to a collection. Here is my cypress/plugins/index.js:
module.exports = (on, config) => {
on("task", {
"defaults:db": () => {
const {dropCollection, createUser } = require("../../lib/connectDB");
dropCollection("users");
createUser(userData)
},
});
};
Here is my /lib/connecDB.js:
export function dropCollection(collection) {
return mongoose.connection.dropCollection(collection);
}
export async function createUserInDB(userData) {
await User.create(userData);
}
So when I run the test, I'm getting:
cy.task('defaults:db') failed with the following error:
Unexpected token 'export'
Tried as well importing these function outside the index.js export, but getting same result.
I'd say it is something about export/import. The functions are exported as ES6, and imported as ES5.
I've tried to import the function the ES6 like:
import { dropCollection, createUser } from '../lib/connectDB'
And then export the plugin function also as ES6, but then I get:
Error: The plugins file is missing or invalid.
Your `pluginsFile` is set to `C:\Users\someRoute\cypress\plugins\index.js`, but either the file is missing, it contains a syntax error, or threw an error when required. The `pluginsFile` must be a `.js`, `.ts`, or `.coffee` file.
I've also tried to import required modules outside the function like:
const globalDbUtils = require('../lib/connectDB')
And then use the functions as
globalDbUtils.dropCollection("collectionName")
globalDbUtils.createUser(userData)
But I'm getting last error. I've tried pretty much everything, I tried to import Mongoose models straight, mongo client etc...Also I tried to import just one function and return it (just copy/pasting official doc...) but cannot make it work. I researched for a couple of days getting nothing, I found there is a npm package that helps u doing this, but since cypress allows you to do this by using no more plugins, I'd like to do it with no more tools than cypress itself.
Anyone knows what I am doing wrong?
Thanks in advance!
You need to use require instead of import at the top of your file and when exporting at the bottom use
module.exports = { createUserInDB }
Instead of exporting as you are currently doing.
I'm trying to understand why require works while import does not for an npm package. The package is r7insight_node and allows us to send our logs to their product, Rapid7. When we use require as per their instructions things work fine, but don't when I use import.
Their library has an src/index.js file that looks like:
// Use codependency for dynamically loading winston
const requirePeer = codependency.register(module);
// Import winston
const winston = requirePeer('winston', {optional: true});
const Transport = requirePeer('winston-transport', {optional: true});
// If we have successfully loaded winston (user has it)
// we initialize our InsightTransport
if (winston) {
provisionWinston(winston, Transport);
}
// Logger is default export
module.exports = Logger;
// Export as `bunyanStream` to not break existing integration
module.exports.bunyanStream = buildBunyanStream;
module.exports.provisionWinston = provisionWinston;
My understanding is that require is synchronous and is "computed" whereas import is asynchronous and is NOT "computed" as written here. Is this the reason for why require works while import does not?
Does "computed" mean in that the index.js file is executed and hence the if (winston) block is checked and executed in a require but not in an import? Is there a way to achieve the same using import statements?
Thanks in advance
for the package to work with the ES6 import way, it has to be written to it, it has to be exported as eg:export default Logger and not module.exports = Logger, hope my answer helped you
An example will make my question clearer, say I want to import debug module to my vuejs codes
Debug module export createDebug function like this,
module.exports = require('./browser.js');
...
exports = module.exports = createDebug.debug = createDebug['default'] = createDebug;
function createDebug(namespace) { ... }
When I use import to import debug module, I can give it any name I want, like
import debug from 'debug' // or any name I want, e.g
import debugjs from 'debug'
I understand if export default anonymous function I can then import it with any name I want, but this is not the case here.
So why can I use any name to import it?
---------------- update -----------------
One takeaway from the answer is that import "any name" work for both default export anonymous function and named function.
but this is not the case here.
It kind of is. You are trying to import a module that has no ES6 exports. You are trying to import a CommonJS module. So Babel has to make a decision how to handle that case.
There are two common ways to export something from a CommonJS module:
Assign a property to exports (or module.expoets), for example exports.answer = 42;
Overwrite the value of module.exports, e.g. module.exports = 42;.
In the second case you end up exporting only a single value from the module. That's basically what a default export is (since there can only be one) and that's what you are doing in your code.
So in other words, when importing a CommonJS module via ES6 import statements, then the value of module.exports is used as the default export value.
We can confirm that by looking at how Babel converts the code:
// import foo from 'bar'; becomes
var _bar = require('bar');
var _bar2 = _interopRequireDefault(_bar);
function _interopRequireDefault(obj) {
return obj && obj.__esModule ? obj : { default: obj };
// ^^^^^^^^^^^^^^^^
}
I have a TypeScript file config.ts that will be run with node:
import myDependency = require('my-dependency');
export = {
doSomething = () => {
...
}
}
In other TypeScript file, I can import this file with full type safety:
import config = require('./config');
config.doSomething();
config.doSomethingElse(); // compiler error, this method doesn't exist
Now I want to unit test this script. In order to mock out the dependencies that this script require()s I'm using proxyquire, which lets me provide the values that my script will get when it makes calls to require(). Here's what my test might look like:
import proxyquire = require('proxyquire');
const config = proxyquire('./config', {
'my-dependency': {} // this mocked object will be provided when config.ts asks for `my-dependency`
});
expect(config.doSomething()).to.do.something();
This works fine, except that my config variable is of type any because I'm using proxyquire() in place of require(). TypeScript must give the require() function special treatment to allow it to perform module resolution. Is there a way to tell the TypeScript compiler that proxyquire() should also do module resolution, similar to require()?
I could rewrite config.ts as a class or make it use an interface. Then I would be able to explicitly type the variables in my tests by importing the class/interface definition. But allowing proxyquire() to implicitly type things for me would be far be the easier solution.
There is a workaround - you can get the type of config.ts module by importing actual module and using typeof in a type cast:
import proxyquire = require('proxyquire');
import configType = require('./config');
const config = <typeof configType> proxyquire('./config', {
'my-dependency': {} // this mocked object will be provided when config.ts asks for `my-dependency`
});
config.doSomething();
// config.noSuchMethod(); // does not compile
This is not ideal because you have to import the same module in your test twice - the real one just to get at the type of it and "proxiquired" one to actually use in your tests, and you have to be careful not to mix up the two. But it's pretty simple compared to the task of implementing another variant of module resolution for typescript. Also, when configType is used in this way - for typing only - its import will not even appear in generated javacsript code.