Proxy

/**
 * 支持负数索引的数组
 */
function MinusArray(...items) {
	return new Proxy([...items], {
		get(target, index, proxyInstance) {
			/* 索引归到正数区间 */
			let length = target.length;
      index = Number(index) % length;
      index = index < 0 ? index + length : index
			return target[index];
		}
	});
}

let arr = new MinusArray(1, 2, 3, 4, 5);
console.log('* arr', arr[-1]);