JavaScript Date Object Introduction

Source: Internet
Author: User
Tags date format object getdate numeric value string time and seconds tostring

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



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