no-else-if.md

no-else-if

• Prohibit else if.

Rule Details

• Here's a summary of why else if is disallowed.

else if causes complex nesting

• else if is the syntax sugar for nesting if statements. Using else if causes nesting of conditional branches as many times as you use it.

complex nested structures waste the reader's brain resources

• Complex nested if statements increase the efforts of code reader in following the conditional branches. If every if does not nest, there will be no stacks of if statements in the code reader's mind, so the brain resources will not be wasted.

• In object-oriented programming, conditional branches with if statements can be designed without any nesting. We have decided to prohibit else if so that complex code cannot be easily produced and all engineers can concentrate on precise class design.

How to Refactor to Purge else if

• To use early returns and guard clauses can avoid else if in many cases.

😩 Examples of incorrect code for no-else-if rule:

function method (firstCondition, secondCondition) {
  if (firstCondition) {
    return createReturnValueAs1stCondition()
  } else if (secondCondition) {
    return createReturnValueAs2ndCondition()
  } else {
    return null
  }
}

😆 Examples of correct code for no-else-if rule:

function method (firstCondition, secondCondition) {
  if (firstCondition) {
    return createReturnValueAs1stCondition()
  }

  if (secondCondition) {
    return createReturnValueAs2ndCondition()
  }

  return null
}

• When multiple branches are to be made based on the value of a single variable, it is better to use object hashing.

😩 Examples of incorrect code for no-else-if rule:

function method (condition) {
  if (condition === 'aaa') {
    return 1000
  } else if (condition === 'bbb') {
    return 2000
  } else if (condition === 'ccc') {
    return 3000
  } else {
    return 0
  }
}

😆 Examples of correct code for no-else-if rule:

function method (condition) {
  return objectHash[condition] ?? 0
}

const objectHash = {
  aaa: 1000,
  bbb: 2000,
  ccc: 3000,
}

Version

• Since 0.0.0