# TS2413: '…' index type '…' is not assignable to '…' index type '…'.

> A number index signature's type doesn't fit the string index signature of the same type. Make the number index type a subtype of the string one.

## What it means

Numeric keys are also string keys in JavaScript, so a type with both index signatures needs the
number signature's value type to be assignable to the string signature's value type.

## Example

```ts
export interface Table {
  [key: string]: number;
  [index: number]: string;
}
```

## How to fix

- Make the number index type assignable to the string index type (here both `number`, or the string one `number | string`).
- Drop one of the signatures if both kinds of key should hold the same type.

Source: https://ts-r.dev/errors/TS2413/