---
url: https://masyaka.github.io/injecute/errors/class-not-constructed.md
description: A class was called without new
---

# `INJECUTE_CLASS_NOT_CONSTRUCTED`

**A class was called without new.**

## How to fix it

Classes compiled to ES5 (Babel for old browsers, TypeScript target: es5) and bound classes cannot be detected. Register them with construct(MyClass).

## Why it happens

Native classes are detected and constructed with `new`. Two kinds of classes look like plain functions:

* classes **compiled to ES5** (Babel targeting old browsers, TypeScript `target: es5`, prebuilt ES5
  libraries in `node_modules`);
* **bound** classes (`MyClass.bind(null)`).

The container calls them without `new`, and the engine throws, for example "Class constructor X cannot be
invoked without 'new'" (V8), "Cannot call a class constructor without |new|" (JavaScriptCore) or "Cannot
call a class as a function" (Babel).

## Fix

```ts
import { construct } from 'injecute';

app.addSingleton('client', construct(LegacyClient), ['config']);
```

An ES5 constructor that has no prototype methods and never uses `this` cannot be detected at all: it
resolves to `undefined`. Use `construct()` for it too.

## Handling it in code

```ts
import { InjecuteError } from 'injecute';

try {
  // ...
} catch (error) {
  if (error instanceof InjecuteError && error.code === 'INJECUTE_CLASS_NOT_CONSTRUCTED') {
    // error.message explains what happened; error.path is the resolution chain
  }
}
```

[All error codes](./index.md)