增加日期 Object 而不转换为 Javascript 中的纪元

Question

Is it possible to increment a date object by one day without converting the object to an epoch number?

For example the traditional way will convert the date object to an epoch number:

var today = new Date();
var tomorrow = new Date(today.valueOf()); // copy date object without converting to epoch
tomorrow.setDate(tomorrow.getDate() + 1); // now gets converted to epoch :'(

Answer 1

The set* methods don't "convert to epoch number", they modify the date's internal time value and return the modified value. The date object is still a date.

 let today = new Date(); today.setHours(0,0,0,0); // Start of day let tvToday = +today; let tomorrow = new Date(today); // setDate adjusts the time value and returns it let tvTomorrow = tomorrow.setDate(tomorrow.getDate() + 1); console.log('Today\'s date: ' + today.toDateString()); console.log('Today\'s time value: ' + tvToday); console.log('Tomorrow\'s date: ' + tomorrow.toDateString()); console.log('Tomorrow\'s time value: ' + tvTomorrow); // May vary from 24 by up to 1 hour depending on crossing DST boundaries console.log('Difference in hours: ' + ((tvTomorrow - tvToday)/3.6e6));

If you want a method that adds a day and returns a new Date object, write a function, maybe named addDays , that takes a date and number of days to add and returns a new Date object with the days added. Lots of libraries have such functions, they're not hard to write.

Answer 2

Not sure if you can do that without converting. Maybe convert back after.

 var today = new Date(); var tomorrow = new Date(today.valueOf()); const x = tomorrow.setDate(tomorrow.getDate() + 1); console.log(x) //epoch const z = new Date(x) console.log(z.toString())