Date API
1. Create Date Object
1.1. Date()
new Date()
new Date(milliseconds)
new Date(dateString)
new Date(year, month, day, hours, minutes, seconds, milliseconds)
JS counts months from 0 to 11. January is 0. December is 11.
// Way 1: new Date()
var d = new Date();
// Way 2: new Date(milliseconds)
var d = new Date(86400000); //Fri Jan 02 1970 08:00:00 GMT+0800 (台北標準時間)
// Way 3: new Date(dateString)
var d = new Date("March 25, 2015 11:13:00"); //Wed Mar 25 2015 11:13:00 GMT+0800 (台北標準時間)
var d = new Date("2015-03-25"); //(ISO Date, The International Standard)
var d = new Date("2015/03/25");
var d = new Date("03/25/2015");
var d = new Date("Mar 25 2015");
var d = new Date("25 Mar 2015");
var d = new Date("Wednesday March 25 2015");
var d = new Date("2015-03");
var d = new Date("2015");
//.....etc.
//Omitting T or Z in a date-time string can give different result in different browser.
var d = new Date("2015-03-25T12:00:00Z"); // T: separating Date and time; Z: UTC time
var d = new Date("2015-03-25T12:00:00-06:30"); //relative to UTC (+HH:MM or -HH:MM)
//Some browsers will error
var d = new Date("2015-3-25"); //with no leading zeroes
var d = new Date("2015/03/25"); //YYYY/MM/DD
var d = new Date("25-03-2015"); //DD-MM-YYYY
// Way 4: new Date(year, month, day, hours, minutes, seconds, milliseconds)
//counts months from 0 to 11. January is 0. December is 11.
var d = new Date(99, 5, 24, 11, 33, 30, 500); //Thu Jun 24 1999 11:33:30 GMT+0800 (台北標準時間)
var d = new Date(99, 5, 24, 11, 33, 30); //Thu Jun 24 1999 11:33:30 GMT+0800 (台北標準時間)
var d = new Date(99, 5, 24, 11, 33); //Thu Jun 24 1999 11:33:00 GMT+0800 (台北標準時間)
var d = new Date(99, 5, 24, 11); //Thu Jun 24 1999 11:00:00 GMT+0800 (台北標準時間)
var d = new Date(99, 5, 24); //Thu Jun 24 1999 00:00:00 GMT+0800 (台北標準時間)
var d = new Date(99, 5); //Tue Jun 01 1999 00:00:00 GMT+0800 (台北標準時間)
var d = new Date(99); //Thu Jan 01 1970 08:00:00 GMT+0800 (台北標準時間) (incorrect)
2. Parsing Dates
2.1. Date.parse()
convert a valid date string to milliseconds
mynote: 覺得和 new Date(string) 的用途極類似，轉成 millisecond 反而多一層工
var msec = Date.parse("March 21, 2012");
var d = new Date(msec);
3. Is Date
Refer to: Array API - Self-Defined isArray() via constructor
4. To String
4.1. (directly stringify object)
4.2. toString()
4.3. toUTCString()
4.4. toDateString()
var d = new Date();
console.log( d ); //Tue Dec 05 2017 19:29:54 GMT+0800 (台北標準時間)
console.log( d.toString() ); //Tue Dec 05 2017 19:29:54 GMT+0800 (台北標準時間)
//The toUTCString() method converts a date to a UTC string (a date display standard).
console.log( d.toUTCString() ); //Tue, 05 Dec 2017 11:29:54 GMT
console.log( d.toDateString() ); //Tue Dec 05 2017
5. Getting (a part of a Date)
var d = new Date("March 25, 2015 11:13:05.800");
//Getting a part of a Date
console.log( d.getFullYear() ); //2015 (the four digit year) (yyyy)
console.log( d.getMonth() ); //2 (0-11)
console.log( d.getDate() ); //25 (day) (1-31)
console.log( d.getDay() ); //3 (weekday) (0-6) 0=Sunday
console.log( d.getHours() ); //11 (0-23)
console.log( d.getMinutes() ); //13 (0-59)
console.log( d.getSeconds() ); //5 (0-59)
console.log( d.getMilliseconds() ); //800 (0-999)
console.log( d.getTime() ); //1427253180000 (milliseconds since January 1, 1970)
6. Setting (a part of a Date)
mynote:
- Setting methods just like void setter. The object will be changed.
- There is still returned value. Note that will return timestamp(number), not a Date object.
var d = new Date('2015-03-25T12:30:05.800');
console.log( typeof d ); //"object"
console.log( typeof d.setFullYear(20201, 0, 14) ); //"number"
Setting Example:
var d = new Date('2015-03-25T12:30:05.800');
d.setFullYear(2020); //Set the year (optionally month and day)
d.setFullYear(2020, 5);
d.setFullYear(2020, 5, 15);
d.setDate(1); //Set the day as a number (1-31)
d.setHours(23); //Set the hour (0-23)
d.setMilliseconds(440); //Set the milliseconds (0-999)
d.setMinutes(33); //Set the minutes (0-59)
d.setMonth(1); //Set the month (0-11)
d.setSeconds(33); //Set the seconds (0-59)
d.setTime(1580571213440); //Set the time (milliseconds since January 1, 1970)
console.log(d); // "Sat Feb 01 2020 23:33:33 GMT+0800 (台北標準時間)"
7. UTC Getting
Same as Getting Methods, , but returns the UTC date
getUTCDate() //Same as getDate(), but returns the UTC date
getUTCDay() //Same as getDay(), but returns the UTC day
getUTCFullYear() //Same as getFullYear(), but returns the UTC year
getUTCHours() //Same as getHours(), but returns the UTC hour
getUTCMilliseconds() //Same as getMilliseconds(), but returns the UTC milliseconds
getUTCMinutes() //Same as getMinutes(), but returns the UTC minutes
getUTCMonth() //Same as getMonth(), but returns the UTC month
getUTCSeconds() //Same as getSeconds(), but returns the UTC seconds
8. Add Days
The
setDate()method can also be used to add days to a date:
var d = new Date('2015-01-10T12:30:05.800');
console.log(d); // "Sat Jan 10 2015 12:30:05 GMT+0800 (台北標準時間)"
d.setDate( 50 ); //將日期部分設50，超過當月天數的部分自動進位到下個月
console.log(d); // "Thu Feb 19 2015 12:30:05 GMT+0800 (台北標準時間)"
d.setDate( d.getDate() + 50 ); //從指定日期往上加50天，如果超過當月天數，一樣自動進位
console.log(d); // "Fri Apr 10 2015 12:30:05 GMT+0800 (台北標準時間)"
9. Compare Dates
Directly comparing
var today = new Date();
var someday = new Date();
someday.setFullYear(2100, 0, 14);
if (someday > today) {
text = "Today is before January 14, 2100.";
} else {
text = "Today is after January 14, 2100.";
}
10. Format
EX:
var date = new Date(value);
return date.getFullYear() + '/' + (date.getMonth() + 1) + '/' + date.getDate();