# required

## Effect

Restrict the detect value is not `undefined | null`.

If strict mode is turned on***(strict=true)***, restrict the detected value is not `undefined | null | {}`.

## Arguments

* `[strict]` ***(boolean)*** - Whether turn on strict mode, default is `false`, means no-strict mode. You can exactly set `strict` to `true` to turn on strict mode.

## Example

```javascript
const schema1 = racoon.object();
schema1.validate(undefined); // pass, return: undefined
schema1.validate(null); // pass, return: null
schema1.validate({}); // pass, return: {}

const schema2 = racoon.object().required();
schema2.validate(undefined); // fail
schema2.validate(null); // fail
schema2.validate({}); // pass

const schema3 = racoon.object().required(true);
schema3.validate(undefined); // fail
schema3.validate(null); // fail
schema3.validate({}); // fail
```