Destructure objects so that defaults can be given for nulls, too.

withoutNulls.ts

type OmitNull<T> = T extends null ? Exclude<T, null> | undefined : T;
type OmitNullProps<T extends object> = { [Key in keyof T]: OmitNull<T[Key]> };

/**
 * Allow destructuring an object, turning any null properties into undefined so
 * a default can be given. If the given object may be null/undefined, then every
 * property may be undefined.
 * 
 * Useful for assigning defaults for properties that may be null. In a usual destructuring
 * assignment, nulls are passed through so you can't provide a default for that case:
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment#default_value
 */
export function withoutNulls<T extends object>(value: T): OmitNullProps<T>;
export function withoutNulls<T extends object>(
  value: T | null | undefined,
): Partial<OmitNullProps<T>>;
export function withoutNulls(value: unknown) {
  return Object.fromEntries(
    Object.entries(value || {}).filter(kv => kv[1] !== null),
  );
}

// DEMO

const foo = {
  string1: 'String',
  string2: 'String',
  maybeNull1: 'maybeNull' as string | null,
  maybeNull2: 'maybeNull' as string | null,
};

// ✓ Possibilities of null are replaced by undefined.
const {
  string1,
  maybeNull1,
} = withoutNulls(foo);

// ✓ If the given object may be null/undefined then everything might be undefined.
const {
  string2,
  maybeNull2,

  // ✓ Unrecogniged keys flagged as errors.
  unrecognized,
} = withoutNulls(null as typeof foo | null);