← Back to rules

eslint/for-direction Correctness

✅ This rule is turned on by default.

⚠️ 🛠️ A dangerous auto-fix is available for this rule.

What it does

Disallow for loops where the update clause moves the counter in the wrong direction, preventing the loop from reaching its stop condition.

Why is this bad?

A for loop with a stop condition that can never be reached will run infinitely. While infinite loops can be intentional, they are usually written as while loops. More often, an infinite for loop is a bug.

Examples

Examples of incorrect code for this rule:

/* for-direction: "error" */

for (var i = 0; i < 10; i--) {}

for (var i = 10; i >= 0; i++) {}

for (var i = 0; i > 10; i++) {}

for (var i = 0; 10 > i; i--) {}

const n = -2;
for (let i = 0; i < 10; i += n) {}

Examples of correct code for this rule:

/* for-direction: "error" */

for (var i = 0; i < 10; i++) {}

for (var i = 0; 10 > i; i++) {
  // with counter "i" on the right
}

for (let i = 10; i >= 0; i += this.step) {
  // direction unknown
}

for (let i = MIN; i <= MAX; i -= 0) {
  // not increasing or decreasing
}

How to use

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)

{
  "rules": {
    "for-direction": "error"
  }
}

Config (oxlint.config.ts)

import { defineConfig } from "oxlint";

export default defineConfig({
  rules: {
    "for-direction": "error",
  },
});

CLI

oxlint --deny for-direction

Version

This rule was added in v0.0.3.

References

• Rule Source
• Upstream rule docs
• Open rule in Oxc Playground