"Sometimes clarity trumps brevity. Write for humans first, machines second."

Disallow useless for loops (no-avoidable-loop)

💼 This rule is enabled in the following configs: 🌐 all, ✅ recommended.

🔧 This rule is automatically fixable by the --fix CLI option.

📖 Rule details

Use repeated statements instead of loops to enhance clarity. Writing out each iteration explicitly ensures that the number of operations is immediately evident in the codebase, rather than being obscured by potentially misleading loops that can conceal significant complexity. Moreover, loops are prone to off-by-one errors, which can introduce unintended bugs.

💡 Examples

// ❌ Incorrect
for (let i = 0; i < 10; i++) console.log('Hello world!')

// ✅ Correct
console.log('Hello world!')
console.log('Hello world!')
console.log('Hello world!')
console.log('Hello world!')
console.log('Hello world!')
console.log('Hello world!')
console.log('Hello world!')
console.log('Hello world!')
console.log('Hello world!')
console.log('Hello world!')

const array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

// ❌ Incorrect
let duplicatedPair
for (let i = 0; i < arr.length; i++) // is this a few operations or thousands?
  for (let j = i + 1; j < arr.length; j++)
    for (let k = 0; k < arr.length; k++)
      for (let l = k + 1; l < arr.length; l++)
        if (i !== k && j !== l && arr[i] === arr[k] && arr[j] === arr[l])
          duplicatedPair = [arr[i], arr[j]]

// ✅ Correct
function hasDuplicate(arr: [V, V, V, V]): boolean {
  // clearly see the complexity
  if (arr[0] === arr[1]) return true
  if (arr[0] === arr[2]) return true
  if (arr[0] === arr[3]) return true
  if (arr[1] === arr[2]) return true
  if (arr[1] === arr[3]) return true
  if (arr[2] === arr[3]) return true
  return false
}

🔗 See also

• eslint-plugin-unicorn/no-for-loop

🔧 Config

{ rules: { 'ninja/no-avoidable-loop': 1 } }

🧑‍💻 Demo