第 55 题：某公司 1 到 12 月份的销售额存在一个对象里面

let obj = {1:222, 2:123, 5:888};
obj.length = 12;
let _obj = Array.from(obj).slice(1);
let newObj =  _obj.map((item) => {if(item === undefined) {return null;} else {return item;}});
console.log(newObj);

let obj = {1:222, 2:123, 5:888};
obj.length = 12;
obj[Symbol.iterator] = Array.prototype[Symbol.iterator];
let _obj = [...obj].slice(1);
let newObj =  _obj.map((item) => {if(item === undefined) {return null;} else {return item;}});
console.log(newObj);

let _obj = [].slice.call(obj);