video-ad-sdk/src/adUnit/helpers/fetch/fetchHtml.ts

VAST/VPAID SDK that allows video ads to be played on top of any player

class FetchError extends Error {
  response?: Response

  public constructor(message: string) {
    super(message)
    this.name = 'FetchError'
    Object.setPrototypeOf(this, FetchError.prototype)
  }
}

const isValidContentType = (contentType: string): boolean => {
  const normalisedCT = contentType.toLowerCase()

  return ['text/plain', 'text/html'].some((allowedType) =>
    normalisedCT.includes(allowedType)
  )
}

const BAD_REQUEST = 400

export const fetchHtml = async (endpoint: string): Promise<string> => {
  const response = await fetch(endpoint)
  const contentType = response.headers.get('Content-Type')

  if (response.status >= BAD_REQUEST) {
    const error = new FetchError(response.statusText)

    error.response = response
    throw error
  }

  if (!contentType || !isValidContentType(contentType)) {
    const error = new FetchError(
      `fetchHtml error, invalid Content-Type ${contentType}`
    )

    error.response = response
    throw error
  }

  return response.text()
}