fetcher.ts

export default async function fetcher<T = unknown>(
  input: RequestInfo,
  init?: RequestInit
): Promise<T> {
  const response = await fetch(input, init)
  const data = await response.json() as T

  if (response.ok) {
    return data
  }

  throw new FetchError({
    message: response.statusText,
    response,
    data
  })
}

export class FetchError extends Error {
  response: Response
  data: unknown

  constructor({
    message,
    response,
    data
  }: {
    message: string
    response: Response
    data: unknown
  }) {
    super(message)

    if (Error.captureStackTrace) {
      Error.captureStackTrace(this, FetchError)
    }

    this.name = 'FetchError'
    this.response = response
    this.data = data ?? { message }
  }
}

index.ts

import fetcher, { FetchError } from './utils/fetcher'

interface User {
  id: number
  name: string
}

async function bootstrap() {
  try {
    const res = await fetcher<User>('https://..')
    console.log(res.id)
  } catch (err) {
    if (err instanceof FetchError) {
      console.log(err.message)
    }
  }
}

bootstrap()