Zod ってなんだっけ。TypeScript に欠かせないらしいよ。

import { z } from 'zod'

const userSchema = z.object({
  name: z.string(),
  age: z.number(),
  tel: z.string(),
})

userSchema.parse({ name: 'hoge', age: 66, tel: 'xxx-xxxx-xxxx' })

const optionalString = z.string().optional()
// string | undefined

const nullableString = z.string().nullable()
// string | null

const nullishString = z.string().nullish()
// string | null | undefined

const userSchema  = z.object({
  name: z.string(),
  age: z.number(),
  tel: z.string(),
})

type user = z.infer<typeof userSchema>

import { z } from 'zod'

// 文字列のスキーマの作成
const stringScheme = z.string()

stringScheme.parse("hoge")
// => "hoge"
stringScheme.parse(12)
// => throws ZodError

import { z } from 'zod'

const stringScheme = z.string()

stringScheme.safeParse(12);
// => { success: false; error: ZodError }

stringSchema.safeParse("hoge");
// => { success: true; data: 'hoge' }

import { z } from 'zod';

const optionalTrimmedString = z.string().trim().optional().default('');

export const postPayloadSchema = z.object({
    title: z.string().trim().min(1, 'Title is required.').max(200, 'Title is too long.'),
    content: z.string().trim().min(1, 'Content is required.'),
    excerpt: optionalTrimmedString
        .refine((value) => value.length <= 300, 'Excerpt is too long.')
        .transform(normalizeNullableText),
    coverImage: optionalTrimmedString
        .refine(
            (value) => value.length === 0 || z.url().safeParse(value).success,
            'Cover image must be a valid URL.'
        )
        .transform(normalizeNullableText),
    tags: optionalTrimmedString
        .refine((value) => value.length <= 200, 'Tags are too long.')
        .transform(normalizeTags),
    published: z.boolean(),
});

export const postsQuerySchema = z.object({
    published: z.enum(['true', 'false']).optional(),
});

export type PostPayload = z.infer<typeof postPayloadSchema>;