Why is this an issue?

Most checks against an indexOf value compare it with -1 because 0 is a valid index. Checking against > 0 ignores the first element, which is likely a bug.

let arr = ["blue", "red"];

if (arr.indexOf("blue") > 0) { // Noncompliant
  // ...
}

Moreover, if the intent is merely to check the presence of the element, and if your browser version supports it, consider using includes instead.

let arr = ["blue", "red"];

if (arr.includes("blue")) {
  // ...
}

This rule raises an issue when an indexOf value retrieved from an array is tested against > 0.

Resources

Documentation

• MDN web docs - Array.prototype.includes()