流：将多个字符串的并集类型转换为新类型

Question

说我有这种类型：

export type VerificationStatus = | 'TRIAL_DEPOSIT_PENDING' | 'TRIAL_DEPOSIT_REQUIRED' | 'TRIAL_DEPOSIT_EXPIRED' | 'TRIAL_DEPOSIT_VERIFICATION_FAILED' | 'TRIAL_DEPOSIT_REINITIATE' | 'VERIFIED';

我有一个哈希映射，看起来可能像这样：

verificationStatus: { trial_deposit_expired: 'Sorry, trial deposits have expired.' },

etc，其中每个键值对的名称应为上面的并集之一，并转换为小写。如何将其设置为VerificationMapKey类型，以便我可以做：const verificationStatus: {[name: VerificationMapKey]: string}？

换句话说，VerificationMapKey是一个函数的返回类型，该函数对VerificationStatus的所有可能值进行迭代并将其变为小写。

Answer 1

简单为：

const VerificationStatuses = ['TRIAL_DEPOSIT_PENDING',
  'TRIAL_DEPOSIT_REQUIRED',
  'TRIAL_DEPOSIT_EXPIRED',
  'TRIAL_DEPOSIT_VERIFICATION_FAILED',
  'TRIAL_DEPOSIT_REINITIATE',
  'VERIFIED'];

const VerificationStausMessagesKey = VerificationStatuses.forEach(status => status.toLowerCase());

export type VerificationStatus = $Keys<typeof VerificationStatuses>;
export type VerificationStausMessageKey = $Keys<typeof VerificationStausMessagesKey>;