src/third_party/mozjs-45/js/src/jit-test/modules/isEven.js

import { isOdd } from "isOdd.js"

export function isEven(x) {
    if (x < 0)
        throw "negative";
    if (x == 0)
        return true;
    return isOdd(x - 1);
}

assertEq(isEven(4), true);
assertEq(isOdd(5), true);