focusOn(value)

ts
function focusOn<T>(value: T): DataOptic<T, {}, T>;
function focusOn<T>(): PureOptic<T, {}, T>;

ts
function focusOn<T>(value: T): DataOptic<T, {}, T>;
function focusOn<T>(): PureOptic<T, {}, T>;

Focus on a value to return a DataOptic.