prefer-for-of.md

prefer-for-of

Prefer a ‘for-of’ loop over a standard ‘for’ loop if the index is only used to access the array being iterated.

This rule recommends a for-of loop when the loop index is only used to read from an array that is being iterated.

Rule Details

For cases where the index is only used to read from the array being iterated, a for-of loop is easier to read and write.

Examples of code for this rule:

❌ Incorrect

for (let i = 0; i < arr.length; i++) {
  console.log(arr[i]);
}

✅ Correct

for (const x of arr) {
  console.log(x);
}

for (let i = 0; i < arr.length; i++) {
  // i is used to write to arr, so for-of could not be used.
  arr[i] = 0;
}

for (let i = 0; i < arr.length; i++) {
  // i is used independent of arr, so for-of could not be used.
  console.log(i, arr[i]);
}

Options

// .eslintrc.json
{
  "rules": {
    "@typescript-eslint/prefer-for-of": "warn"
  }
}

This rule is not configurable.

When Not To Use It

If you transpile for browsers that do not support for-of loops, you may wish to use traditional for loops that produce more compact code.

Related To

• TSLint: 'prefer-for-of'

Attributes

• Configs:
  • ✅ Recommended
  • 🔒 Strict
• 🔧 Fixable
• 💭 Requires type information