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I'm having the following TypeScript class

export class Vehicule extends TrackableEntity {
  vehiculeId: number;
  constructor() {
    super();
    return super.proxify(this);
  }
}

my typescript target in tsconfig.json is configured as es6:

"compilerOptions": {
    "module": "es2015",
    "moduleResolution": "node",
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "target": "es6",
}

At runtime, here in Chrome, the code is failing with:

ReferenceError: Cannot access 'Vehicule' before initialization
    at Module.Vehicule (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:10559:100)
    at Module../src/app/domain/models/VehiculeGpsBoxInfo.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:11156:69)
    at __webpack_require__ (https://localhost:44338/runtime.js:84:30)
    at Module../src/app/domain/models/Vehicule.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:10571:78)
    at __webpack_require__ (https://localhost:44338/runtime.js:84:30)
    at Module../src/app/components/dispositifsDATI/mainDATI/listDATI/listDATIponent.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:6447:82)
    at __webpack_require__ (https://localhost:44338/runtime.js:84:30)
    at Module../src/app/components/dispositifsDATI/index.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:3053:95)
    at __webpack_require__ (https://localhost:44338/runtime.js:84:30)
    at Module../src/app/components/dispositifsDATI/dispositifsDATI.routes.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:2982:64)

I needed to change es5 to es6 to solve this other problem.

---

EDIT: The VehiculeGpsBoxInfo.ts file is importing Vehicule like this:

import { Vehicule } from "./Vehicule";

EDIT 2: I vould say that this may be webpack related, the way that modules are exported/imported in the genrated modules.

EDIT 3: After further research, this seems to have nothing to do with the code shown above. Started a new question about webpack and ES6.

I'm having the following TypeScript class

export class Vehicule extends TrackableEntity {
  vehiculeId: number;
  constructor() {
    super();
    return super.proxify(this);
  }
}

my typescript target in tsconfig.json is configured as es6:

"compilerOptions": {
    "module": "es2015",
    "moduleResolution": "node",
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "target": "es6",
}

At runtime, here in Chrome, the code is failing with:

ReferenceError: Cannot access 'Vehicule' before initialization
    at Module.Vehicule (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:10559:100)
    at Module../src/app/domain/models/VehiculeGpsBoxInfo.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:11156:69)
    at __webpack_require__ (https://localhost:44338/runtime.js:84:30)
    at Module../src/app/domain/models/Vehicule.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:10571:78)
    at __webpack_require__ (https://localhost:44338/runtime.js:84:30)
    at Module../src/app/components/dispositifsDATI/mainDATI/listDATI/listDATI.component.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:6447:82)
    at __webpack_require__ (https://localhost:44338/runtime.js:84:30)
    at Module../src/app/components/dispositifsDATI/index.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:3053:95)
    at __webpack_require__ (https://localhost:44338/runtime.js:84:30)
    at Module../src/app/components/dispositifsDATI/dispositifsDATI.routes.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:2982:64)

I needed to change es5 to es6 to solve this other problem.

---

EDIT: The VehiculeGpsBoxInfo.ts file is importing Vehicule like this:

import { Vehicule } from "./Vehicule";

EDIT 2: I vould say that this may be webpack related, the way that modules are exported/imported in the genrated modules.

EDIT 3: After further research, this seems to have nothing to do with the code shown above. Started a new question about webpack and ES6.

• javascript
• angular
• typescript
• webpack
• es6-class

Share Improve this question Follow edited Jul 4, 2019 at 9:18 asked Jul 3, 2019 at 12:55 anonanon 3

• Is it valid to return something in a constructor? – jlang Commented Oct 31, 2019 at 10:08
• 2 @jlang Please see this – anon Commented Oct 31, 2019 at 10:32
• I had this issue and found out a service I was injecting had some injections missing providers. Check your tree – Polyterative Commented May 11, 2022 at 12:16

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16 Answers 16

Sorted by: Reset to default 109

I was getting this error due to a circular dependency, like

• A injected with B
• B injected with C
• C injected with A

Removing the circular dependecy fixed this error.

You're probably running into this Angular issue: https://github.com/angular/angular-cli/issues/15077.

From that issue:

Hi, is there a reason why you need emitDecoratorMetadata to be true?

This TypeScript option has a fundamental design limitation with ES2015+ code and is best avoided when targeting such output. As such this is an issue with TypeScript itself and not Angular.

Angular 8+ no longer requires the option. It was also previously only required for JIT mode which is typically only used in development.

The solution is to set "emitDecoratorMetadata": false in your tsconfig.json file.

Side note: I must say, given that previous versions of the Angular CLI automatically added emitDecoratorMetadata: true, and there's no reason I can see why a dev should know that emitDecoratorMetadata should now be false, it's pretty horrible that the Angular team basically said "this isn't our problem" and closed the issue without action. This could have been easily "fixed" by adding some better documentation (as pointed out by someone in the linked issue).

to find circular dependencies :

npx madge --circular --extensions ts ./

(build before)

Note that this error can also be caused by defining two public @Injectable classes within the same .ts file.

I've tripped over this more than once when I'm just prototyping stuff locally (especially when refactoring one service into multiple).

Setting emitDecoratorMetadata: false does fix this situation as well; but in case you're in a hurry to fix something or don't want fiddle with thetsconfig.json file on a large project - it's useful to know that you might be able to fix it by just moving one of the classes into a new file.

I ran into this due to the order of my import statements in the module. A file that also accessed the component had to be imported before the component.

I see that in 2023 there is no correct answer, but this problem is listed high enough in google. So basically what you need to do in scenario:

• A injected with B
• B injected with C
• C injected with A

Put all tree components in one separate module.ts e.g. abc.module.ts. In that file you can event simpler put all components in array like this:

export const components = [ AComponent, BComponent, CComponent, ];

and then in @NgModule {} add this array to: exports: [components], declarations: [components],

imports:[] array has all dependant components which are used by those tree. And thats it, you will be safe from ReferenceError : Cannot access 'X' before initialization

For people landing here from a search: When you get this error in Angular 15 or above, it might be due to circular dependencies at standalone components. In that case you can fix it with forwardRef:

@Component({
  standalone: true,
  selector: 'app-b',
  templateUrl: './b.component.html',
  styleUrls: ['./b.scss'],
  imports: [
    forwardRef(() => AComponent))
  ]
})
export class BComponent implements OnInit {

}

See: https://stackoverflow.com/a/76233363/11603006

Circular dependency is the devil!

It causes the whole dependency loop to be unresolvable by the compiler. In most cases, the errors look like you are not importing the classes at all.

Some might think that circular dependencies should only be prevented in services and modules, However, circular dependency should be prevented in all forms, even in models, components, and classes.

When you have circular dependency it's a sign that (sooner or later) you need to refactor and restructure your code. The following hints might be useful to do so. Suppose we want to remove the circular dependency between two classes A, B.

Solution 1: Union/Merge

A and B are following the very same concept and they can be merged into a single class.

Solution 2: Separation/Creation

There should be a new class C, that both A and B rely on or sits somewhere between those two.

According to my experience, in most cases, the circular dependency happens because the developer tends to merge n logics into k (k<n) classes.

In Angular 8, having entryComponents declared as an empty list in a SharedModule caused this issue for me:

entryComponents: []

After removing entryComponents, everything worked fine.

In my case, I had an index.ts file that exported components from A.ts and B.ts.

B.ts tried to import from the index.ts instead of A.ts.

This caused the MJS to be emitted in the incorrect order because of the cycle:

B.ts -> index.ts -> B.ts

You can search for imports ending in from ".". This can be avoided by using a underscored prefix _index.ts (except in the root directory).

I'm posting this for others looking for other ideas that cause Cannot access 'X' before initialization. Best of luck.

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