CODEWITHSUNDEEP
typesflowtype
Spencer Bigum
Spencer Bigum

Reputation: 1931

Flow type array undefined

I'm having trouble performing operations on an array item using .split() because FLOW thinks it COULD be undefined.

export const getTokenFromCookieRes = (cookies: string[]): mixed => {

  if (!cookies) {
    return undefined
  }

  if (0 in cookies) {
    return cookies[0] // cookies[0] returns an error for possibly being undefined
      .split(';')
      .find(c => c.trim().startsWith('jwt='))
      .split('=')[1]
  } else {
    return undefined
  }
}

tryflow

Upvotes: 0

Views: 349

Answers (1)

adrice727
adrice727

Reputation: 1492

The issue is not that cookies[0] might be undefined; it's that the result of find() could be undefined. You need to check the results of find() before trying to call split() on the string.

const getTokenFromCookieRes = (cookies?: string[]): mixed => {

  if (!cookies) {
    return undefined
  }

  if (!!cookies[0]) {
    const jwt = cookies[0] // No issues here
      .split(';')
      .find(c => c.trim().startsWith('jwt='))
      return jwt && jwt.split('=')[1];
  } 
}

Upvotes: 3

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