# oxc/const-comparisons

> Disallow comparisons that are always true, always false, or repeated

A condition such as `age > 65 && age < 18` can never be true, so the code behind it never runs. It's usually a swapped operator, a swapped number, or a copied line that nobody edited.

The rule reports:

- Two comparisons of the same value with numbers, joined by `&&`, that can't both be true: `age > 65 && age < 18`.
- Two comparisons like that where one already implies the other: `age > 18 && age > 65`.
- A value compared with itself using `<`, `<=`, `>` or `>=`: `count < count`.
- The same expression on both sides of `&&` or `||`: `isOpen && isOpen`, `a === b || b === a`.
- An expression and its opposite: `isOpen && !isOpen`, `a === b || a !== b`.

Two calls never count as the same expression, because each call can return something else.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"oxc/const-comparisons" = "error" # or "warn"
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad {"count": 3} */}
```js
if (age > 65 && age < 18) {
  addDiscount();
}

if (status >= 400 && status >= 500) {
  retry();
}

while (index < index) {
  index++;
}
```

{/* bad {"count": 2} */}
```js
const ready = loaded && loaded;
const known = role === "admin" || role !== "admin";
```

Not reported:

{/* good */}
```js
if (age > 65 || age < 18) {
  addDiscount();
}

if (status >= 500) {
  retry();
}

while (index < length) {
  index++;
}

const ready = loaded && visible;
const known = role === "admin" || role === "editor";
const twoLeft = queue.pop() && queue.pop();
```