# isBoolean

```typescript
isBoolean
```

Verifies if provided `Verificable` represents a boolean value. Only boolean values (`true`, `false`) are matching, meaning that 'truthy'/'falsey' values are not matching this `Predicate`.

### Possible errors:

#### If provided `Verificable` is not a boolean:

```typescript
{
    type: "isBoolean",
    path: [/* ... */]
}
```

### Examples:

Each of examples uses this import statement:

```typescript
const { asVerificable, isValid, isBoolean } = require("verifica");
```

#### Null or undefined is not considered a boolean:

```typescript
const verificable = asVerificable(null);
isValid(verificable, isBoolean); // false
```

#### String value is not considered a boolean as well:

```typescript
const verificable = asVerificable("true");
isValid(verificable, isBoolean); // false
```

#### `true` and `false` are considered boolean values:

```typescript
const verificable = asVerificable(false);
isValid(verificable, isBoolean); // true
```