Function isNotUndefined

isNotUndefined<T>(u: T): u is RelaxedExclude<T, undefined>
Type guard that checks if a value is not undefined.

Type Narrowing Behavior:
- Excludes undefined from the input type when true
- Preserves all other types in the union
- Commonly used to filter out undefined values
Type Parameters
- T
  The type of the input value
Parameters
- u: T
  The value to check
Returns u is RelaxedExclude<T, undefined>
true if u is not undefined, false otherwise. When true, TypeScript excludes undefined from the type.
Example
```
const values: (number | undefined)[] = [1, undefined, 2];

const definedValues = values.filter(isNotUndefined);

assert.deepStrictEqual(definedValues, [1, 2]);
```
- Defined in src/guard/is-type.mts:49