TS7030

error TS7030: Not all code paths return a value.

Broken Code ❌

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function getFlightType(type: 1 | 2) {
  if (type === 1) {
    return 'Return trip';
  }
}

Fixed Code ✔️

TypeScript reminds us that we forgot to return a value in case our if-condition doesn’t match. We can solve this problem in many ways.

Always return a value:

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function getFlightType(type: 1 | 2) {
  if (type === 1) {
    return 'Return trip';
  }
  return 'One way';
}

Add general else:

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function getFlightType(type: 1 | 2) {
  if (type === 1) {
    return 'Return trip';
  } else {
    return 'One way';
  }
}

Handle all cases:

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function getFlightType(type: 1 | 2) {
  switch (type) {
    case 1:
      return 'Return trip';
    case 2:
      return 'One way';
  }
}

Add default case:

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function getFlightType(type: 1 | 2) {
  switch (type) {
    case 1:
      return 'Return trip';
    default:
      return 'One way';
  }
}

Define that the return type can be void:

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function getFlightType(type: 1 | 2): string | void {
  if (type === 1) {
    return 'Return trip';
  }
}

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