Answer 1

let arr22 = [1, 2, 3, 4, 5, 6, 7];
const find02 = (arr, k) => {
return arr.splice(arr.length - k).concat(arr)
}

Answer 2

感谢分享，学到了很多！
建议在简单实现一个createstore函数的演示部分中补充上reducer的代码

const reducer = (state = {}, action = {type: 'INIT'}) => {
    switch (action.type) {
        case 'INCREMENT': {
            return Object.assign( {}, { count: ++state.count })
        }
        default: return { count: 0 };
    }
}

// 为了能直接看到count，可以顺便可以修改下render方法的渲染值
const render = () => {
    document.body.innerText = store.getState().count;
}