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.

Options

No options available for this rule.

Examples

Examples of incorrect code for this rule:

/* eslint 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:

/* eslint 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 in the CLI or using the config file, you can use:

CLI

oxlint --deny for-direction

Config (.oxlintrc.json)

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

References

• Rule Source