[API reference](https://evolu.dev/docs/api-reference) › [@evolu/common](https://evolu.dev/docs/api-reference/common) › [Types](https://evolu.dev/docs/api-reference/common/Types) › Predicate

```ts
type Predicate<T> = (value: T) => boolean;
```

Defined in: [packages/common/src/Types.ts:54](https://github.com/evoluhq/evolu/blob/e7144e2bbe9069362b62dec1b64a8aa922b8f1b0/packages/common/src/Types.ts#L54)

Checks a condition on a value and returns a boolean.

A predicate starts with an 'is' prefix, e.g., `isEven`.

### Example

```ts
const isEven: Predicate<number> = (n) => n % 2 === 0;

const numbers = [1, 2, 3, 4];
const evenNumbers = numbers.filter(isEven); // [2, 4]
```