Develop Reference

Mocha / Webpack: Cannot use import statement outside a module

I'm new to Node and JS Testing. I have a web applications w/ Webpack as a bundler. I have some entry point JS's which are included into the page. The entry points are using module files like this:
export default function() {
...
}
Now I would like to Unit test this module. I have picked up Mocha but it is not critical to me. Could be Jest or anything else.
I wrote a very simple test.js like this. It it not doing anything but tests if the entire setup works:
import foo from '../js/someModuleOfMine'
const assert = require('assert')
describe('Test Suite', () => {
it('should at least run', () => {
assert.equal(true, true)
})
})
executing mocha from CLI gives me this error:
import foo from '../js/someModuleOfMine'
^^^^^^
SyntaxError: Cannot use import statement outside a module
Adhering to some advises I have tired to add "type": "module" to my package.json but it only changed error to something even more obscure:
Error: Not supported
I am definitely missing something obvious but I cannot comprehend what.

Not sure if it will help the OP, but I had the same problem and it was due to typescript. I solved in this way:
install ts-node:
npm install ts-node --save-dev
add the require line in the mocha config (I have it in the package.json, but one can also have it in the .mocharc.json file):
"mocha": {
"spec": "./**/*test.ts",
"ignore": "./node_modules/**",
"require": "ts-node/register/files",
"timeout": 20000
}

Ruby on Rails 6 Webpack with Javascript libraries

I am building a new project in Rails 6. I have a front-end library I want to use (#tarekraafat/autocomplete.js) that is installed by yarn and exists in my node_modules directory, but is not being made available to other JS code in the browser. Here is what I have set up currently:
/package.json:
"dependencies": {
"#tarekraafat/autocomplete.js": "^8.2.1"
}
/app/javascript/packs/application.js:
import "#tarekraafat/autocomplete.js/dist/js/autoComplete.min.js"
/app/views/.../example.html.erb
<script type="text/javascript">
window.onload = () => {
new autoComplete({
[...]
});
};
</script>
I am getting an error in the browser pointing to the new autoComplete():
Uncaught ReferenceError: autoComplete is not defined
Some reading seems to indicate that I need to modify the /config/webpack/environment.js file, in which I have tried various versions of the following with no luck (including restarting the dev server):
/config/webpack/environment.js:
const { environment } = require('#rails/webpacker')
const webpack = require('webpack')
environment.plugins.prepend('Provide',
new webpack.ProvidePlugin({
autoComplete: 'autocomplete.js'
})
);
module.exports = environment
First, what do I need to do to add this library so it can be used correctly? Second, as someone who has not directly used webpack previously, what is the function of adding this definition to the environments.js file, and why don't I need to do it for some libraries (bootstrap, popper) but I do for others (jquery, and maybe autocomplete.js)?

In Webpacker, the usage of this library would be as follows:
// app/javascript/src/any_file.js
import autoComplete from "#tarekraafat/autocomplete"
new autoComplete(...)
// app/javascript/packs/application.js
import "../src/any_file"
This alone does not import the autoComplete variable into the global scope. To do that, the simplest thing is assign the variable to window from within your webpack dependency graph.
// app/javascript/src/any_file.js
import autoComplete from "#tarekraafat/autocomplete"
window.autoComplete = autoComplete
As an aside, you don't need to use the ProvidePlugin configuration for this library. The ProvidePlugin says: “add this import to all files in my dependency graph.” This might be helpful for something like jQuery to make legacy jQuery plugins work in webpack. It is not necessary to make your autocomplete lib work

Require.js define object is somehow being inserted to my code - gulp.js

I'm running a gulp-concat script, which concats jquery, slick-carousel, t.js and my index.js files.
const pack = () => {
return gulp.src(['./node_modules/jquery/**/jquery.js', './node_modules/slick-carousel/**/slick.js', './assets/js/t.js-master/t.js', './js/index.js'])
// .pipe(gulp_babel({
// 'presets': ['#babel/env'],
// 'plugins': ["transform-remove-strict-mode"]
// }))
.pipe(gulp_concat('main.js'))
// .pipe(gulp_uglify())
.pipe(gulp.dest('./build'));
}
As you can see, I removed any pipes that might be causing the issue. The only task running is gulp-concat. (index.js is all in ES5 and I'm running on latest version of firefox, no need for babel atm) When I open my page, however, I get the error
Uncaught ReferenceError: define is not defined
Looking at main.js, I found a define object at the end of the jquery section - but only in the concatinated file, not the jquery in node_modules. I didn't add this, and I'm not using require.js as far as I know:
define( [
"./core",
"./selector",
"./traversing",
"./callbacks",
"./deferred",
"./deferred/exceptionHook",
"./core/ready",
"./data",
"./queue",
"./queue/delay",
"./attributes",
"./event",
"./event/focusin",
"./manipulation",
"./manipulation/_evalUrl",
"./wrap",
"./css",
"./css/hiddenVisibleSelectors",
"./serialize",
"./ajax",
"./ajax/xhr",
"./ajax/script",
"./ajax/jsonp",
"./ajax/load",
"./core/parseXML",
"./core/parseHTML",
"./effects",
"./effects/animatedSelector",
"./offset",
"./dimensions",
"./deprecated",
"./exports/amd",
"./exports/global"
], function( jQuery ) {
"use strict";
return jQuery;
} ); // jQuery seems to end here
How is this extra code being added, and how might I avoid it? I'm also using browserSync, but don't think that's related.

I've just checked the source of jQuery and there is a file:
https://github.com/jquery/jquery/blob/3.5.1/src/jquery.js
So what you need to do is to simply exclude it and it should fix the issue :)

How to properly load local AMD modules with jspm/system.js

I am having a really hard time using local AMD modules in an Aurelia project that uses es6, JSPM, and system.js. I am hoping someone out there can help me configure my project to enable me to import/load my AMD modules and use them in my project. The local AMD style modules are in a format similar to the following:
define
(['require',
'lib/alerts/STARTSTOP',
'lib/alerts/STOPPED',
...
],
function( require, STARTSTOP, STOPPED, ... ) {
return {
alert: function( data ) {
var type = data.type;
var ev = data.event;
var cls = require( 'lib/alerts/' + ev );
return new cls( data );
}
};
});
When I try to import/load this module into an es6 module I am running into the following error: Uncaught TypeError: Unexpected anonymous AMD define.. I get this error when trying to load the module in either of the following ways:
System.import('lib/alerts/AlertFactory').then( (m) => {
console.log( m );
});
or
import AlertFactory from 'lib/alerts/AlertFactory.js';
I have also made sure to add the following script to my index.html:
<script>
window.define = System.amdDefine;
window.require = window.requirejs = System.amdRequire;
</script>
In addition to the above I have also added a meta format property to my config.js file, but that hasn't seemed to help either.
meta: {
...
"lib/alerts/*.js": {
"format": "amd"
}
}
Does anyone have any ideas on why I am running into the error I am seeing and how to properly load my modules? I appreciate any help/insight you can offer.
UPDATE
I finally realized that the main issue here is that I'm trying to use existing AMD modules in and Aurelia project, and the default Aurelia gulp build assumes that all code is written in ES6 and not mixed with AMD. That's why I'm having issues. Vanilla jspm/system.js handle a mix of module formats, but Aurelia does not out of the box.

Just put your AMD modules out of src so babel will not be able to transpile it. Here is working solution I use to import jquery modules:
First, I have local_packages folder in project root and I have jquery module local_packages/somelib/js/mymodule.js
Then in config.js
paths: {
...
"local/*": "local_packages/*",
}
map: {
...
"somelib": "local/somelib",
"somelib1": "/local_packages/somelib1",
}
And finally my import looks like: import 'somelib/js/mymodule';

Why do I see "define not defined" when running a Mocha test with RequireJS?

I am trying to understand how to develop stand-alone Javascript code. I want to write Javscript code with tests and modules, running from the command line. So I have installed node.js and npm along with the libraries requirejs, underscore, and mocha.
My directory structure looks like this:
> tree .
.
├── node_modules
├── src
│   └── utils.js
└── test
└── utils.js
where src/utils.js is a little module that I am writing, with the following code:
> cat src/utils.js
define(['underscore'], function () {
"use strict";
if ('function' !== typeof Object.beget) {
Object.beget = function (o) {
var f = function () {
};
f.prototype = o;
return new f();
};
}
});
and test/utils.js is the test:
> cat test/utils.js
var requirejs = require('requirejs');
requirejs.config({nodeRequire: require});
requirejs(['../src/utils'], function(utils) {
suite('utils', function() {
test('should always work', function() {
assert.equal(1, 1);
})
})
});
which I then try to run from the top level directory (so mocha sees the test directory):
> mocha
node.js:201
throw e; // process.nextTick error, or 'error' event on first tick
^
Error: Calling node's require("../src/utils") failed with error: ReferenceError: define is not defined
at /.../node_modules/requirejs/bin/r.js:2276:27
at Function.execCb (/.../node_modules/requirejs/bin/r.js:1872:25)
at execManager (/.../node_modules/requirejs/bin/r.js:541:31)
...
So my questions are:
Is this the correct way to structure code?
Why is my test not running?
What is the best way to learn this kind of thing? I am having a hard time finding good examples with Google.
Thanks...
[sorry - momentarily posted results from wrong code; fixed now]
PS I am using requirejs because I also want to run this code (or some of it) from a browser, later.
Update / Solution
Something that is not in the answers below is that I needed to use mocha -u tdd for the test style above. Here is the final test (which also requires assert) and its use:
> cat test/utils.js
var requirejs = require('requirejs');
requirejs.config({nodeRequire: require});
requirejs(['../src/utils', 'assert'], function(utils, assert) {
suite('utils', function() {
test('should always work', function() {
assert.equal(1, 1);
})
})
});
> mocha -u tdd
.
✔ 1 tests complete (1ms)

The reason your test isn't running is because src/utils.js is not a valid Node.js library.
According to the RequireJS documentation, in order to co-exist with Node.js and the CommonJS require standard, you need to add a bit of boilerplate to the top of your src/utils.js file so RequireJS's define function is loaded.
However, since RequireJS was designed to be able to require "classic" web browser-oriented source code, I tend to use the following pattern with my Node.js libraries that I also want running in the browser:
if(typeof require != 'undefined') {
// Require server-side-specific modules
}
// Insert code here
if(typeof module != 'undefined') {
module.exports = whateverImExporting;
}
This has the advantage of not requiring an extra library for other Node.js users and generally works well with RequireJS on the client.
Once you get your code running in Node.js, you can start testing. I personally still prefer expresso over mocha, even though its the successor test framework.

The Mocha documentation is lacking on how to set this stuff up, and it's perplexing to figure out because of all the magic tricks it does under the hood.
I found the keys to getting browser files using require.js to work in Mocha under Node: Mocha has to have the files added to its suites with addFile:
mocha.addFile('lib/tests/Main_spec_node');
And second, use beforeEach with the optional callback to load your modules asynchronously:
describe('Testing "Other"', function(done){
var Other;
beforeEach(function(done){
requirejs(['lib/Other'], function(_File){
Other = _File;
done(); // #1 Other Suite will run after this is called
});
});
describe('#1 Other Suite:', function(){
it('Other.test', function(){
chai.expect(Other.test).to.equal(true);
});
});
});
I created a bootstrap for how to get this all working: https://github.com/clubajax/mocha-bootstrap

You are trying to run JS modules designed for browsers (AMD), but in the backend it might not work (as modules are loaded the commonjs way). Because of this, you will face two issues:
define is not defined
0 tests run
In the browserdefine will be defined. It will be set when you require something with requirejs. But nodejs loads modules the commonjs way. define in this case is not defined. But it will be defined when we require with requirejs!
This means that now we are requiring code asynchronously, and it brings the second problem, a problem with async execution.
https://github.com/mochajs/mocha/issues/362
Here is a full working example.
Look that I had to configure requirejs (amd) to load the modules, we are not using require (node/commonjs) to load our modules.
> cat $PROJECT_HOME/test/test.js
var requirejs = require('requirejs');
var path = require('path')
var project_directory = path.resolve(__dirname, '..')
requirejs.config({
nodeRequire: require,
paths: {
'widget': project_directory + '/src/js/some/widget'
}
});
describe("Mocha needs one test in order to wait on requirejs tests", function() {
it('should wait for other tests', function(){
require('assert').ok(true);
});
});
requirejs(['widget/viewModel', 'assert'], function(model, assert){
describe('MyViewModel', function() {
it("should be 4 when 2", function () {
assert.equal(model.square(2),4)
})
});
})
And for the module that you want to test:
> cat $PROJECT_HOME/src/js/some/widget/viewModel.js
define(["knockout"], function (ko) {
function VideModel() {
var self = this;
self.square = function(n){
return n*n;
}
}
return new VideModel();
})

Just in case David's answer was not clear enough, I just needed to add this:
if (typeof define !== 'function') {
var define = require('amdefine')(module);
}
To the top of the js file where I use define, as described in RequireJS docs ("Building node modules with AMD or RequireJS") and in the same folder add the amdefine package:
npm install amdefine
This creates the node_modules folder with the amdefine module inside.

I don't use requirejs so I'm not sure what that syntax looks like, but this is what I do to run code both within node and the browser:
For imports, determine if we are running in node or the browser:
var root = typeof exports !== "undefined" && exports !== null ? exports : window;
Then we can grab any dependencies correctly (they will either be available already if in the browser or we use require):
var foo = root.foo;
if (!foo && (typeof require !== 'undefined')) {
foo = require('./foo');
}
var Bar = function() {
// do something with foo
}
And then any functionality that needs to be used by other files, we export it to root:
root.bar = Bar;
As for examples, GitHub is a great source. Just go and check out the code for your favorite library to see how they did it :) I used mocha to test a javascript library that can be used in both the browser and node. The code is available at https://github.com/bunkat/later.