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0x800a1391 - JavaScript runtime error: 'module' is not defined

I am from a C++ background and have a day's experience in TypeScript. I am trying to implement a design (interface/class) that is split between multiple files. It is flashing runtime error : 0x800a1391 - JavaScript runtime error: 'module' is not defined
Info.ts
export = Test; <----------- 0x800a1391 - JavaScript runtime error: 'module' is not defined
namespace Test {
export class Info {
}
}
TestWrapper.ts
import { Info } from "./Info";
namespace Test {
class TestWrapper {
public GetInfo(): Info {
return this.m_info;
}
}
}
Am I using something in the wrong way?

A guess:
export = Something
Compiles to something like
module.exports = Something
module.exports is a construct of the so-called "commonjs module system", something that is not available in browsers, but in node.js. So if you run the generated code in a browser through a direct <script> import, it will bring an error like that. TS transpiles imports and exports to module systems that can be specified in the tsconfig.json, but TS itself is not responsible for implementing the module system.
What to do?
If this code is really supposed to run in the browser, you could opt on one of the 2 following options:
Run the code through a module bundler (webpack), which will generate a browser compatible "bundle" (a big JS) concatenating all your files. Webpack has ways of including typescript as a plugin, so that you dont need to make your "build" a 2-step process; Module bundlers are usually fairly complicated.
Make your files module-less (which means: no top-levem imports or exports) and import them through vanilla <script> tags.

Am I using something in the wrong way?
While namespaces are commonly used in other languages, they do not exist in JavaScript, so the typescript version is just some rarely used way to add proper typing to some things (I never used it yet). In your case you actually don't need a namespace. Just:
export default class Info { /*...*/ }
Then you can
import Info from ".Info";
export default class TestWrapper { /*...*/ }
PS: That said, I actually don't know how to make this work with namespaces to resolve the error

It looks like you are trying to mix modules and namespaces. I would suggest reading Namespaces and Modules.
You don't need to to export at the top level using export = Test, you also shouldn't import { Info } from "./Info"; because Info is part of the Test namespace which TestWrapper is a member of.
If you want to go the namespace route, consider:
Info.ts
namespace Test {
export class Info {}
}
TestWrapper.ts
namespace Test {
export class TestWrapper {
m_info: Info;
public GetInfo(): Info {
return this.m_info;
}
}
}
Consumer.ts
console.log(Test.TestWrapper);
Compile this using:
tsc --outFile foo.js Info.ts TestWrapper.ts Consumer.ts
Then run using:
node foo.js
Which prints:
[Function: TestWrapper]

TypeScript: How to import a class from a submodule?

I have a TypeScript app using both .ts and .d.ts files. References are made using the triple slash notation /// <reference path=...>. My app has the following definition file:
declare module APP {
class Bootstrap {
constructor();
}
}
I then declare a module named "app" so I can import it in other files:
declare module "app" {
export = APP;
}
Assuming my Bootstrap class exists, I then import the Bootstrap class using:
import { Bootstrap } from 'app';
This works.
Now I create a submodule on APP, like so:
declare module APP.Service {
class Async {
constructor();
}
}
I make another declaration for the submodule:
declare module "app/service" {
export = APP.Service;
}
Now, when I import the class Async like so:
import { Async } from 'app/service';
I get the following error message:
Module '"app/service"' resolves to a non-module entity and cannot be imported using this construct.``
How do I be import a class from a submodule?
NOTE
I have found a workaround by declaring a global var:
declare var APP_SERVICE: APP.Service.IService; // IService exists
And exporting that on my module:
declare module "app/service" {
export = APP_SERVICE;
}
The downside of this is that my global namespace get's polluted with var's I don't use, because I will use Service through App.Service, not APP_SERVICE.

If you care about creating a nice, reusable, maintainable declaration file for a module, the preferred way is by using typings, as it handles aspects such as type dependency management and submodules very well for you.
Create a separate repository for the typings your are writing.
Add typings.json file with the name and path to your main typings. eg:
{
"name": "my-main-module",
"main": "index.d.ts"
}
Add your the type declarations for your main module to index.d.ts and the type declarations for submodules to submodule-name.d.ts.
submodule.d.ts
export interface submoduleInterface {
someProp: number
}
index.d.ts
import * as submodule from './submodule'
export interface mainInterface {
someProp: number
}
Run typings bundle index.d.ts -o bundle.d.ts. This will bundle all your typings into one type declaration file, declaring the proper submodules and respecting all the necessary dependencies between modules, submodules and even external modules.
Either copy this file to a custom-typings directory in your original project, or submit this repo to the typings registry so other people can also profit from it 🙂, and pull it in with a normal typings i my-module-name.
Here is the gist with all the code, and the resulting bundle.d.ts. Here is a repo that uses both submodules (redux-persist/constants) as external dependencies (redux), and that got ultimately submitted to the typings registry.

TypeScript ES6 import module "File is not a module error"

I am using TypeScript 1.6 with ES6 modules syntax.
My files are:
test.ts:
module App {
export class SomeClass {
getName(): string {
return 'name';
}
}
}
main.ts:
import App from './test';
var a = new App.SomeClass();
When I am trying to compile the main.ts file I get this error:
Error TS2306: File 'test.ts' is not a module.
How can I accomplish that?

Extended - to provide more details based on some comments
The error
Error TS2306: File 'test.ts' is not a module.
Comes from the fact described here http://exploringjs.com/es6/ch_modules.html
17. Modules
This chapter explains how the built-in modules work in ECMAScript 6.
17.1 Overview
In ECMAScript 6, modules are stored in files. There is exactly one
module per file and one file per module. You have two ways of
exporting things from a module. These two ways can be mixed, but it is
usually better to use them separately.
17.1.1 Multiple named exports
There can be multiple named exports:
//------ lib.js ------
export const sqrt = Math.sqrt;
export function square(x) {
return x * x;
}
export function diag(x, y) {
return sqrt(square(x) + square(y));
}
...
17.1.2 Single default export
There can be a single default export. For example, a function:
//------ myFunc.js ------
export default function () { ··· } // no semicolon!
Based on the above we need the export, as a part of the test.js file. Let's adjust the content of it like this:
// test.js - exporting es6
export module App {
export class SomeClass {
getName(): string {
return 'name';
}
}
export class OtherClass {
getName(): string {
return 'name';
}
}
}
And now we can import it in these three ways:
import * as app1 from "./test";
import app2 = require("./test");
import {App} from "./test";
And we can consume imported stuff like this:
var a1: app1.App.SomeClass = new app1.App.SomeClass();
var a2: app1.App.OtherClass = new app1.App.OtherClass();
var b1: app2.App.SomeClass = new app2.App.SomeClass();
var b2: app2.App.OtherClass = new app2.App.OtherClass();
var c1: App.SomeClass = new App.SomeClass();
var c2: App.OtherClass = new App.OtherClass();
and call the method to see it in action:
console.log(a1.getName())
console.log(a2.getName())
console.log(b1.getName())
console.log(b2.getName())
console.log(c1.getName())
console.log(c2.getName())
Original part is trying to help to reduce the amount of complexity in usage of the namespace
Original part:
I would really strongly suggest to check this Q & A:
How do I use namespaces with TypeScript external modules?
Let me cite the first sentence:
Do not use "namespaces" in external modules.
Don't do this.
Seriously. Stop.
...
In this case, we just do not need module inside of test.ts. This could be the content of it adjusted test.ts:
export class SomeClass
{
getName(): string
{
return 'name';
}
}
Read more here
Export =
In the previous example, when we consumed each validator, each module only exported one value. In cases like this, it's cumbersome to work with these symbols through their qualified name when a single identifier would do just as well.
The export = syntax specifies a single object that is exported from the module. This can be a class, interface, module, function, or enum. When imported, the exported symbol is consumed directly and is not qualified by any name.
we can later consume it like this:
import App = require('./test');
var sc: App.SomeClass = new App.SomeClass();
sc.getName();
Read more here:
Optional Module Loading and Other Advanced Loading Scenarios
In some cases, you may want to only load a module under some conditions. In TypeScript, we can use the pattern shown below to implement this and other advanced loading scenarios to directly invoke the module loaders without losing type safety.
The compiler detects whether each module is used in the emitted JavaScript. For modules that are only used as part of the type system, no require calls are emitted. This culling of unused references is a good performance optimization, and also allows for optional loading of those modules.
The core idea of the pattern is that the import id = require('...') statement gives us access to the types exposed by the external module. The module loader is invoked (through require) dynamically, as shown in the if blocks below. This leverages the reference-culling optimization so that the module is only loaded when needed. For this pattern to work, it's important that the symbol defined via import is only used in type positions (i.e. never in a position that would be emitted into the JavaScript).

Above answers are correct. But just in case...
Got same error in VS Code. Had to re-save/recompile file that was throwing error.

How can I accomplish that?
Your example declares a TypeScript < 1.5 internal module, which is now called a namespace. The old module App {} syntax is now equivalent to namespace App {}. As a result, the following works:
// test.ts
export namespace App {
export class SomeClass {
getName(): string {
return 'name';
}
}
}
// main.ts
import { App } from './test';
var a = new App.SomeClass();
That being said...
Try to avoid exporting namespaces and instead export modules (which were previously called external modules). If needs be you can use a namespace on import with the namespace import pattern like this:
// test.ts
export class SomeClass {
getName(): string {
return 'name';
}
}
// main.ts
import * as App from './test'; // namespace import pattern
var a = new App.SomeClass();

In addition to A. Tim's answer there are times when even that doesn't work, so you need to:
Rewrite the import string, using the intellisense. Sometimes this fixes the issue
Restart VS Code

I had this issue and I had forgotten to export the Class.

In addition to Tim's answer, this issue occurred for me when I was splitting up a refactoring a file, splitting it up into their own files.
VSCode, for some reason, indented parts of my [class] code, which caused this issue. This was hard to notice at first, but after I realised the code was indented, I formatted the code and the issue disappeared.
for example, everything after the first line of the Class definition was auto-indented during the paste.
export class MyClass extends Something<string> {
public blah: string = null;
constructor() { ... }
}

Just in case this may works for you as it did form me, i had this files
//server.ts
class Server{
...
}
exports.Server = Server
//app.ts
import {Server} from './server.ts'
And this actually raised an error but i changed server.ts to
//server.ts
export class Server{
...
}
and it worked 😎👌
Note: i am using this config
"target": "esnext",
"module": "commonjs",

I faced the same issue in a module that has no exports. I used it for side-effects only. This is what the TypeScript docs say about importing side-effects modules:
Though not recommended practice, some modules set up some global state that can be used by other modules. These modules may not have any exports, or the consumer is not interested in any of their exports. To import these modules, use:
import "./my-module.js";
In that situation, you can fix the "File is not a module" error by simply exporting an empty object:
// side-effects stuff
export default {};

I faced the same issue ("File is not a module error") for import js in vue component
import handleClientLoad from "../../../public/js/calendar.js"
I do this and solve it
// #ts-ignore
import handleClientLoad from "../../../public/js/calendar.js"

The file needs to add Component from core hence add the following import to the top
import { Component } from '#angular/core';

Typescript, require module as class

I'm using an existing js library that uses AMD modules in my typescript code. I want to use a Javascript class as the base for my Typescript class. This is what I'm trying to do:
famous.js
define('famous/core/View',['require','exports','module'],function(require, exports, module) {
function View() {
...
}
...
module.exports = View;
});
View.d.ts
declare module "famous/core/View" {
}
AppView.ts
import View = require('famous/core/View');
class AppView extends View {
}
export = AppView;
But it says "Cannot find name 'View'". I suppose it's logical it doesn't work since a module is not a class, but I don't know another way.

You need to define a class and use export = in View.d.ts. For example:
declare module "famous/core/View" {
class View {
// TODO define members of View
}
export = View;
}

On further analysis it seems like purely a require configuration problem. It shouldn't have anything to do with class vs module. Are you sure your paths are correct and you have a config.ts require configuration file?

TypeScript: access global var from a class without import

I got this module like this:
module MyModule {
export class Constants {
public static WIDTH:number = 100;
public static HEIGHT:number = 100;
....
}
}
export = MyModule;
Now I need to use MyModule.Constants.WIDTH in another class but I can't use import (I need to deliver this class js to a third party, and they don't use requirejs). Right now I use reference to get code checking but it keep giving this error (at transpilling time)
error TS2095: Could not find symbol 'MyModule'
What should I do now so I can use autocomplete and get rid of this error?

I hope you're not mindplay on the TypeScript forum otherwise I'm about to repeat myself.
export and import work together. You should either be using both or neither. If you check what the generated code looks like with and without the export keyword you'll see that export causes a module to be built. Since the third party can't use RequireJS I don't think this is what you want.
I would structure my classes like the following:
// file pkg/Foo.ts
module company.pkg {
export class Foo {}
}
// file pkg2/Bar.ts
module company.pkg2 {
export class Bar{}
}
Putting everything into the name space of your company minimizes the chance of a conflict with another library. Classes know about each other using a reference /// <reference path="..." /> which will allow it to compile.
Since you're not doing modules I would also compile to a single file using --out filename.js. That gets all the files included in (usually) the right order.