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# Default

Use Default to generate missing properties on a value using default schema annotations if available. This function does not check the value and returns an unknown type. You should Check the result before use. Default is a mutable operation. To avoid mutation, Clone the value first.

```typescript
const T = Type.Object({
  x: Type.Number({ default: 0 }),
  y: Type.Number({ default: 0 }),
});

const X = Value.Default(T, null); // const 'X = null - non-enumerable

const Y = Value.Default(T, {}); // const 'Y = { x: 0, y: 0 }

const Z = Value.Default(T, { x: 1 }); // const 'Z = { x: 1, y: 0 }
```

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