prefer-for-of

Enforces the use of for-of loop over the standard for loop where possible.

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

Attributes

• Included in configs
  • ✅ Recommended
  • 🔒 Strict
• Fixable
  • 🔧 Automated Fixer
  • 🛠 Suggestion Fixer
• 💭 Requires type information

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'