TypeScript TV

TS7030

Not all code paths return a value.

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

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:

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

Add general else:

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

Handle all cases:

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

Add default case:

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

Define that the return type can be void:

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