JavaScript Two Sum Debugging (n time complexity)

I am trying to achieve n-time-complexity for a two sum function via utilization of hashes in JavaScript. I’ve come up with the code below, but for some reason it does not capture all of the paired indices. The function is supposed to return pairs of indices of integers in an array that add up to zero.

Array.prototype.twoSumHash = function () {
    let newArr = [];
    const hash = {};
    this.forEach((ele, idx) => {
        if (hash[ele * -1]) {
            const pair = [hash[ele * -1], idx];
            newArr.push(pair);
        }
        hash[ele] ? hash[ele].push(idx) : hash[ele] = idx;
    });
    return newArr;
};

console.log([1, -1, 2, 3, 4, -2].twoSumHash());

This function only seems to return the 2 and -2 ([2,5]), but not the 1 and -1 ([0, 1]). Please help, and thank you!