import 8.41.0 source

[pve-eslint.git] / eslint / docs / src / rules / constructor-super.md

---
title: constructor-super
rule_type: problem
---

Constructors of derived classes must call `super()`.
Constructors of non derived classes must not call `super()`.
If this is not observed, the JavaScript engine will raise a runtime error.

This rule checks whether or not there is a valid `super()` call.

## Rule Details

This rule is aimed to flag invalid/missing `super()` calls.

Examples of **incorrect** code for this rule:

:::incorrect

```js
/*eslint constructor-super: "error"*/
/*eslint-env es6*/

class A {
    constructor() {
        super();  // This is a SyntaxError.
    }
}

class A extends B {
    constructor() { }  // Would throw a ReferenceError.
}

// Classes which inherits from a non constructor are always problems.
class A extends null {
    constructor() {
        super();  // Would throw a TypeError.
    }
}

class A extends null {
    constructor() { }  // Would throw a ReferenceError.
}
```

:::

Examples of **correct** code for this rule:

:::correct

```js
/*eslint constructor-super: "error"*/
/*eslint-env es6*/

class A {
    constructor() { }
}

class A extends B {
    constructor() {
        super();
    }
}
```

:::

## When Not To Use It

If you don't want to be notified about invalid/missing `super()` callings in constructors, you can safely disable this rule.