negative-index
描述
假设有数组 const arr = [1, 2, 3]
- 允许负数索引，arr[-1] >> 3 arr[-3] >> 1
- 超出返回
undefined，arr[-5] >> undefined
题解
通过 Proxy 拦截 get 方法，修正索引
javascript
function negativeIndex(arr) {
return new Proxy(arr, {
get(target, idx, receiver) {
idx = +idx;
if (idx < 0) {
idx = target.length + idx;
if (idx < 0) return undefined;
}
return Reflect.get(target, idx, receiver);
},
});
}