zod optional/nullable/nullish differences

zod-optional-null.ts

// zod schema
z.object({
    // valid if string or:
    optional: z.string().optional(), // field not provided, or explicitly `undefined`
    nullable: z.string().nullable(), // field explicitly `null`
    nullish: z.string().nullish(), // field not provided, explicitly `null`, or explicitly `undefined`
});

// type
{
    optional?: string | undefined;
    nullable: string | null;
    nullish?: string | null | undefined;
}