js 指定日期添加天数自动变为下年或下月

代码如下

let date = '2021-12-02', n = 2;
let dateOne = new Date(date.replace('-', '/'));
let time = dateOne.getTime() + n * 24 * 3600 * 1000;
let dateTwo = new Date(time);
let startTime = dateTwo.getFullYear() + '-' + (dateTwo.getMonth() + 1) + '-' + dateTwo.getDate() 
console.log(startTime)   //startTime --> 2021-12-04