[Home](./index.md) > [@apextoaster/js-utils](./js-utils.md) > [mustExist](./js-utils.mustexist.md) ## mustExist() function Assert that a variable is not nil and return the value. Signature: ```typescript export declare function mustExist(val: Optional): T; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | val | Optional<T> | | Returns: `T` val ## Exceptions NotFoundError