JavaScript Date Object Introduction

Date and Time objects
1. Introduce

Date object that is the object of the action date and time. A Date object can operate on dates and times only through methods.
2. Constructor function
2.1 New Date (): Returns the current local date and time

Parameters: None

return value:

{Date} returns a Date object that represents the local date and time.

Example:

var dt = new Date ();
Console.log (DT); => returns a Date object that represents the local date and time


2.2 New Date (milliseconds): Converts the number of milliseconds to a Date object

Parameters:

①milliseconds {int}: Number of milliseconds, representing the number of milliseconds to begin stacking from ' 1970/01/01 00:00:00 ' as the starting point.

Note: The time of the beginning of the seconds also add the current time zone, the Times in Beijing East 8 zone, the starting time is actually: ' 1970/01/01 08:00:00 '

return value:

{Date} returns a superimposed date object.

Example:

var dt = new Date (1000 * 60 * 1); The number of milliseconds to advance 1 minutes
Console.log (DT); => {date}:1970/01/01 08:01:00
DT = new Date (-1000 * 60 * 1); Number of milliseconds backwards 1 minutes
Console.log (DT); => {date}:1970/01/01 07:59:00


2.3 New Date (DATESTR): Converts a string to a Date object

Parameters:

①datestr {string}: A string that can be converted to a Date object (can be omitted); There are two main types of strings:

1) yyyy/mm/dd HH:mm:ss (recommended): If you omit the time, the date object returned time is 00:00:00.

2) Yyyy-mm-dd HH:mm:ss: If the time is omitted, the Date object returned is 08:00:00 (plus the local time zone). If you do not omit the time, this string will fail in IE conversion!

return value:

{Date} returns a converted Date object.

Example:

var dt = new Date (' 2014/12/25 '); Yyyy/mm/dd
Console.log (DT); => {DATE}:2014/12/25 00:00:00
DT = new Date (' 2014/12/25 12:00:00 '); YYYY/MM/DD HH:mm:ss
Console.log (DT); => {DATE}:2014/12/25 12:00:00

DT = new Date (' 2014-12-25 '); Yyyy-mm-dd
Console.log (DT); => {date}:2014-12-25 08:00:00 (plus the time zone of the East 8 zone)
DT = new Date (' 2014-12-25 12:00:00 '); Yyyy-mm-dd HH:mm:ss (Note: This conversion method in IE will be an error!) )
Console.log (DT); => {date}:2014-12-25 12:00:00


2.4 New date (year, month, Opt_day, Opt_hours, Opt_minutes, Opt_seconds, opt_milliseconds): convert Date To Date object

Parameters:

①year {int}: year; 4 digits. such as: 1999, 2014

②month {int}: month; 2 digits. Starting from 0, 0 means January, 11 represents December.

③opt_day {int} is optional: number, 2 digits, starting from 1, 1 represents 1th.

④opt_hours {int} optional: time; 2 digits; Value 0~23.

⑤opt_minutes {int} optional: 2 digits; 0~59.

⑥opt_seconds {int} optional: seconds; 2 not digits; 0~59 value.

⑦opt_milliseconds {int} is optional: milliseconds; 0~999 value.

return value:

{Date} returns a converted Date object.

Example:

var dt = new Date (2014, 11); December 2014 (The number of months entered here is 11)
Console.log (DT); => {date}:2014/12/01 00:00:00
DT = new Date (2014, 11, 25); December 25, 2014
Console.log (DT); => {DATE}:2014/12/25 00:00:00
DT = new Date (2014, 11, 25, 15, 30, 40); December 25, 2014 15:30 40 seconds
Console.log (DT); => {DATE}:2014/12/25 15:30:40
DT = new Date (2014, 12, 25); March 25, 2014 (the number of months entered here is 12, for the 13th month, jump to January of the second year)
Console.log (DT); => {DATE}:2015/01/25


3. Property

None of the date objects can operate on dates and times only through methods.


4. Instance method

The instance methods of a Date object are divided into 2 main forms: local time and UTC time. In the same way, there are typically 2 time format operations (method names with UTC, or UTC time), which mainly describes the operation of local time.


4.1 Get method
4.1.1 getFullYear (): Returns the year value of the Date object; 4-bit year.
4.1.2 GetMonth (): Returns the month value of a Date object. Starting from 0, so the real month = Returns the value +1.
4.1.3 GetDate (): Returns the date value in the month of the date object, the range of the value 1~31.
4.1.4 getHours (): Returns a Date object's small value.
4.1.5 getminutes (): Returns the minute value of a Date object.
4.1.6 getseconds (): Returns the number of seconds in a Date object.
4.1.7 getmilliseconds (): Returns the millisecond value of the Date object.
4.1.8 getday (): Returns the week value of the week for the date object, 0 for Sunday, 1 for Monday, 2 for Tuesday, and so on
4.1.9 getTime (): Returns the millisecond value between the Date object and ' 1970/01/01 00:00:00 ' (The time zone in Beijing is East 8, and the starting time is actually: ' 1970/01/01 08:00:00 ').

Example:

Dt.getfullyear (); => 2014: Year
Dt.getmonth (); => 11: Month; actual for December (month starting from 0)
Dt.getdate (); => 25: Day
Dt.gethours (); => 15: When
Dt.getminutes (); => 30: Min
Dt.getseconds (); => 40: Sec
Dt.getmilliseconds (); => 333: MS
Dt.getday (); => 4: The value of the day of the week
Dt.gettime (); => 1419492640333: Returns the millisecond value between the Date object and the ' 1970/01/01 00:00:00 ' (The time zone in Beijing is East 8, and the starting time is actually: ' 1970/01/01 08:00:00 ')


4.2 Set method
4.2.1 setFullYear (year, Opt_month, opt_date): Sets the Date object's age value, 4-bit year.
4.2.2 Setmonth (Month, opt_date): Sets the month value of the Date object. 0 indicates January, 11 represents December.
4.2.3 setdate (date): Sets the date value in the month of the date object; The range of values 1~31.
4.2.4 sethours (Hour, opt_min, Opt_sec, opt_msec): Sets the Date object's small value.
4.2.5 setminutes (min, Opt_sec, opt_msec): Sets the minute value of the Date object.
4.2.6 setseconds (sec, opt_msec): Sets the number of seconds for the date object.
4.2.7 setmilliseconds (msec): Sets the millisecond value of the Date object.


Example:

var dt = new Date ();
Dt.setfullyear (2014); => 2014: Year
Dt.setmonth (11); => 11: Month; actual for December (month starting from 0)
Dt.setdate (25); => 25: Day
Dt.sethours (15); => 15: When
Dt.setminutes (30); => 30: Min
Dt.setseconds (40); => 40: Sec
Dt.setmilliseconds (333); => 333: MS
Console.log (DT); => December 25, 2014 15:30 40 seconds 333 ms


4.3 Other methods
4.3.1 toString (): Converts date to a ' date and time ' string
4.3.2 toLocaleString (): Converts date to a local format string with a ' month and a day '
4.3.3 todatestring (): Converts date to a ' month-day ' string
4.3.4 tolocaledatestring (): Converts date to a local format string of ' year/month '
4.3.5 totimestring (): convert date to a ' time and seconds ' string
4.3.6 tolocaletimestring (): convert date to a local format string of ' time and seconds '
4.3.7 valueof (): As with gettime (), returns the millisecond value between the Date object and ' 1970/01/01 00:00:00 ' (The time zone in Beijing is East 8, and the starting time is actually: ' 1970/01/01 08:00:00 ')
Example:

var dt = new Date ();
Console.log (Dt.tostring ()); => Tue Dec 2014 22:56:11 gmt+0800 (China Standard Time): convert date to a ' date and time ' string
Console.log (Dt.tolocalestring ()); => December 23, 2014 10:56:11: Converts date to a local format string with a ' month and a day '

Console.log (Dt.todatestring ()); => Tue Dec 23 2014: convert date to a ' month-day ' string
Console.log (Dt.tolocaledatestring ()); => December 23, 2014: Converts date to a local format string of ' year/month '

Console.log (Dt.totimestring ()); => 22:56:11 gmt+0800 (China Standard Time): convert date to a ' time and seconds ' string
Console.log (Dt.tolocaletimestring ()); => 10:56:11: Converts date to a local format string of ' time and seconds '

Console.log (Dt.valueof ()); => returns the millisecond value between the Date object and ' 1970/01/01 00:00:00 ' (The time zone in Beijing is East 8, and the starting time is actually: ' 1970/01/01 08:00:00 ')


5. Static method
5.1 Date.now ()

Description: Returns the millisecond value between the Date object and the ' 1970/01/01 00:00:00 ' (The time zone in Beijing is East 8, and the starting time is actually: ' 1970/01/01 08:00:00 ')

Parameters: None

return value:

{int}: The number of milliseconds between the current time and the start time.

Example:
Console.log (Date.now ()); => 1419431519276


5.2 Date.parse (DATESTR)

Description: Converts a string to a Date object and returns the millisecond value between this Date object and ' 1970/01/01 00:00:00 ' (The time zone in Beijing is East 8, and the starting time is actually: ' 1970/01/01 08:00:00 ')

Parameters:

①datestr {string}: A string that can be converted to a Date object (can be omitted); There are two main types of strings:

1) yyyy/mm/dd HH:mm:ss (recommended): If you omit the time, the date object returned time is 00:00:00.

2) Yyyy-mm-dd HH:mm:ss: If the time is omitted, the Date object returned is 08:00:00 (plus the local time zone). If you do not omit the time, this string returns Nan (not a number) in IE!

return value:

{int} returns the number of milliseconds between the converted Date object and the start time.

Example:

Console.log (Date.parse (' 2014/12/25 12:00:00 ')); => 1419480000000
Console.log (Date.parse (' 2014-12-25 12:00:00 ')); => 1419480000000 (Note: This conversion method returns nan! in IE )


6. Actual operation
6.1 C # 's datetime type to the Date object of JS

Description: The datetime type of C # is returned to the foreground by JSON serialization in the format: "\/date (1419492640000) \/". The middle number that represents the number of milliseconds between the value of datetime and the start time.

Example:

Background code: Simple ASHX

public void ProcessRequest (HttpContext context) {
System.Web.Script.Serialization.JavaScriptSerializer js = new System.Web.Script.Serialization.JavaScriptSerializer ();
DateTime dt = DateTime.Parse ("2014-12-25 15:30:40");
String rs = js. Serialize (DT); Serialized as JSON
Context. Response.ContentType = "Text/plain";
Context. Response.Write (RS);
}

Foreground code:

var datetimejsonstr = ' \/date (1419492640000) \/'; JSON format for C # datetime type conversions
var msecstr = datetimejsonstr.tostring (). replace (/\/date\ ([-]?\d+) \) \//gi, "$"; => ' 1419492640000 ': Get the millisecond string by regular substitution
var msesint = Number.parseint (MSECSTR); The millisecond string is converted to a numeric value
var dt = new Date (msesint); Initializing the Date Object
Console.log (Dt.tolocalestring ()); => December 25, 2014 3:30:40


6.2 Get the Countdown

Description: Calculates the current time from the target time difference how many days.

Example:

/**
* Back to Countdown
* @param dt {Date}: Destination Date object
* @return {Strin}: Back to Countdown: X-day x Time X
*/
function Getdowntime (DT) {
1. Get the countdown
var intervalmsec = Dt-date.now (); The target time minus the current time to get the difference in the number of milliseconds
var intervalsec = intervalmsec/1000; Convert to number of seconds
var day = parseint (INTERVALSEC/3600/24); Days
var hour = parseint ((intervalsec-day * 24 * 3600)/3600); Hours
var min = parseint ((intervalsec-day * 3600-hour * 3600)/60); Minutes

2. If the difference of milliseconds is less than 0, indicating that the target time is less than the current time, then the value is negative:-X-day-time-points, display, only the number of days before the negative on the line.
if (Intervalmsec < 0) {
hour = 0-hour;
min = 0-min;
}

3. Stitching string and returning
var rs = day + ' days ' + hour + ' when ' + min + ' min ';
Return RS;
}

Current time: 2014/12/28 13:26
Console.log (Getdowntime) (New Date (' 2015/06/01 ')); => 154 days 10:33
Console.log (Getdowntime) (New Date (' 2014/01/01 ')); =>-361 Days 13:26


6.3 Compare the size of 2 date objects

Note: You can compare the number of milliseconds between 2 and the start time to distinguish between sizes.

Example:

var dt1 = new Date (' 2015/12/01 ');
var dt2 = new Date (' 2015/12/25 ');
Console.log (Dt1 > DT2); => false