oxc/const-comparisons

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.

Configure#

Off by default. To turn it on:

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

Examples#

if (age > 65 && age < 18) {
  addDiscount();
}

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

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

const ready = loaded && loaded;
const known = role === "admin" || role !== "admin";

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();