仅限Javascript - 需要更好的方法将日期格式化为yyyymmdd而不使用jquery或其他库

I need my date to be in ccyymmdd format to add a day and pass over to a cobol application via xml. I also need to convert the new date with the added day to mm/dd/ccyy format to place into my slickgrid. My boss believes there has to be an easier way however, I can't seem to find one without using jquery or adding another library. Here is the code I am using;I need my date to be in ccyymmdd format to add