What's this function doing?

function negArray(arr) {
    return Proxy.create({
        set: function (proxy, index, value) {
            index = parseInt(index);
            return index < 0 ? (arr[arr.length + index] = value) : (arr[index] = value);
        },
        get: function (proxy, index) {
            index = parseInt(index);
            return index < 0 ? arr[arr.length + index] : arr[index];
        }
    });
};
system
What's this function doing?

function negArray(arr) {
    return Proxy.create({
        set: function (proxy, index, value) {
            index = parseInt(index);
            return index < 0 ? (arr[arr.length + index] = value) : (arr[index] = value);
        },
        get: function (proxy, index) {
            index = parseInt(index);
            return index < 0 ? arr[arr.length + index] : arr[index];
        }
    });
};
user
The negArray function creates a proxy around a provided array that behaves like the array but allows retrieving and setting values with negative indexes.
assistant
<|system|>
</s>
<|user|>
What's this function doing?

function negArray(arr) {
    return Proxy.create({
        set: function (proxy, index, value) {
            index = parseInt(index);
            return index < 0 ? (arr[arr.length + index] = value) : (arr[index] = value);
        },
        get: function (proxy, index) {
            index = parseInt(index);
            return index < 0 ? arr[arr.length + index] : arr[index];
        }
    });
};</s>
<|assistant|>
The negArray function creates a proxy around a provided array that behaves like the array but allows retrieving and setting values with negative indexes.</s>
