The previous words
The Date object is a built-in data type in the JavaScript language and is used to provide an operation interface for dates and times. The Date object is created based on the java.util.Date class in early java. For this reason, the Date type uses milliseconds elapsed from 0:00 on January 1, 1970 to save the date. The time range it can represent is 100 million days each around 0:00 on January 1, 1970. This article will introduce the usage of Date objects in detail
Static methods Before introducing the constructor of the Date object, we will first introduce the static methods. Because the static method of the Date object is closely related to its constructor. The process of creating a Date object using a constructor is similar to the process of using a static method wearing a coat
There are three static methods in the Date object, namely Date.now(), Date.parse(), and Date.UTC(). These methods are called through the Date() constructor itself, rather than through the Date instance object
Date.now()
ECMAScript5 has added the now() method, which returns the number of milliseconds from the current time to 0:00 UTC on January 1, 1970. This method does not support passing parameters
[Note] This method returns the Number numeric type
console.log(Date.now());//1468297046050console.log(Date.now('2016,1,1'));//1468297046050console.log(typeof Date.now());//'number'In browsers that do not support the Date.now() method, you can use the + operator to convert the Date object into a number, and similar effects can be achieved.
console.log(new Date());//Tue Jul 12 2016 12:21:33 GMT+0800 (China Standard Time)console.log(+new Date());//1468297293433console.log(+new Date(2000,1,1));//949334400000
This method is often used to analyze code
var start = Date.now();doSomething();var stop = Date.now();result = stop - start;
Date.parse()
This method is used to parse a date string. The parameter is a string containing the date and time to be parsed, returning the number of milliseconds from 0:00 on January 1, 1970 to the given date
This method parses the format of the string according to the date and time string format rules . In addition to the standard format, the following formats are also supported. If the string is not recognized, NaN will be returned
1. 'Month/Day/Year', as 6/13/2004
2. 'Month, Day, Year' such as January 12,2004 or Jan 12,2004
3. 'Week, month, day, year, time: minute, second time zone' Tue May 25 2004 00:00:00 GMT-0700
[Note] The browser does not support string formats that do not represent dates but only time.
console.log(Date.parse('6/13/2004'));//1087056000000console.log(Date.parse('January 12,2004'));//1073836800000console.log(Date.parse('Tue May 25 2004 00:00:00 GMT-0700'));//1085468400000console.log(Date.parse('2004-05-25T00:00:00'));//1085443200000console.log(Date.parse('2016'));//1451606400000console.log(Date.parse('T00:00:00'));//NaNconsole.log(Date.parse());//NaN[Note] In ECMAScript5, if a string using the standard date-time string format rule has a prefix of 0 before math, it will be parsed as UTC time, and if the time is not prefixed as 0, it will be parsed as local time. Other situations are generally resolved to local time
console.log(Date.parse('7/12/2016'));//1468252800000console.log(Date.parse('2016-7-12'));//1468252800000console.log(Date.parse('2016-07-12'));//1468281600000Date.UTC()
Date.UTC() also returns the number of milliseconds of a given date, but its parameters are not a string, but numerical parameters representing year, month, day, hour, minute, second, and millisecond respectively.
Date.UTC(year, month, day, hours, minutes, seconds, ms), year and month parameters are fixed, and the remaining parameters are optional. See here for details on the date and time format rules.
Because the function has 7 formal parameters, its length value is 7
console.log(Date.UTC.length);//7
[Note] This method uses UTC time, not local time
console.log(Date.UTC(1970));//NaNconsole.log(Date.UTC(1970,0));//0console.log(Date.UTC(1970,0,2));//86400000console.log(Date.UTC(1970,0,1,1));//36000000console.log(Date.UTC(1970,0,1,1,59));//714000console.log(Date.UTC(1970,0,1,1,59,30));//717000
Constructor Date() constructor has up to 5 ways to use it
【0】Date()
Numbers can be called like a function without the new operator. It will ignore all incoming parameters and return a string representation of the current date and time
Date();
[Note] Since the Date() function does not use operators, it cannot be actually called a constructor
console.log(Date());//"Tue Jul 12 2016 13:38:41 GMT+0800 (China Standard Time)"console.log(Date('2016/1/1'));//"Tue Jul 12 2016 13:38:41 GMT+0800 (China Standard Time)"console.log(typeof Date());//'string'【1】When the Date() function uses the new operator and does not have parameters, a Date object will be created based on the current time and date
new Date();
console.log(new Date());//Tue Jul 12 2016 13:41:45 GMT+0800 (China Standard Time)console.log(new Date);//Tue Jul 12 2016 13:41:45 GMT+0800 (China Standard Time)console.log(typeof new Date());//'object'
【2】Date() function can accept a numeric parameter, which represents the number of milliseconds between the set time and 0 o'clock on January 1, 1970
new Date(milliseconds);
console.log(new Date(0));//Thu Jan 01 1970 08:00:00 GMT+0800 (China Standard Time)console.log(new Date(86400000));//Fri Jan 02 1970 08:00:00 GMT+0800 (China Standard Time)console.log(typeof new Date(0));//object
【3】The Date() function can accept a string parameter, and the parameter form is similar to the Date.parse() method. But the parse() method returns a number, while the Date() function returns an object
new Date(datestring);console.log(new Date('6/13/2004'));//Sun Jun 13 2004 00:00:00 GMT+0800 (China Standard Time)console.log(Date.parse('6/13/2004'));//10870560000000console.log(typeof new Date(6/13/2004));//objectconsole.log(typeof Date.parse(6/13/2004));//numberThe processing of prefixed 0 in the standard date and time string is also similar to the Date.parse() method. If there is prefixed 0, it is equivalent to UTC time, and if there is no, it is equivalent to local time. The rest are usually local time
console.log(new Date('7/12/2016'));//Tue Jul 12 2016 00:00:00 GMT+0800 (China Standard Time)console.log(new Date('2016-7-12'));//Tue Jul 12 2016 00:00:00 GMT+0800 (China Standard Time)console.log(new Date('2016-07-12'));//Tue Jul 12 2016 08:00:00 GMT+0800 (China Standard Time)【4】 The Date() function can accept parameters similar to those of the Date.UTC() method, but the Date.UTC() method returns a number of milliseconds and is UTC time, while the Date() function returns an object and is local time
console.log(new Date(2016,7,12));//Fri Aug 12 2016 00:00:00 GMT+0800 (China Standard Time)console.log(+new Date(2016,7,12));//14709312000000console.log(typeof new Date(2016,7,12));//'object'console.log(Date.UTC(2016,7,12));//14709600000000console.log(typeof Date.UTC(2016,7,12));//'number'
[Note] When using a method similar to the Date.parse() function, if the date object is out of range, the browser will automatically calculate the date into a value within the range; when using a method similar to the Date.UTC() function, if the date object is out of range, the browser will prompt Invalid Date
console.log(new Date(2016,7,32));//Thu Sep 01 2016 00:00:00 GMT+0800 (China Standard Time)console.log(new Date(2016,8,1));//Thu Sep 01 2016 00:00:00 GMT+0800 (China Standard Time)console.log(new Date('2016-8-32'));//Invalid Dateconsole.log(new Date('2016-9-1'));//Thu Sep 01 2016 00:00:00 GMT+0800 (China Standard Time)Example method
The Date object has no properties that can be read and written directly, and all accesses to dates and times need to be passed through methods. Most methods of Date objects are divided into two forms: one is to use local time and the other is to use UTC time, which are listed together below. For example, get[UTC]Day() represents both getDay() and getUTCDay()
There are 46 instance methods in the Date object, which can be divided into the following 3 categories: to class, get class, and set class
【to class】
The to class method returns a string from the Date object, indicating the specified time
toString()
Returns the date string of the local time zone
toUTCString()
Returns the date string of UTC time
toISOString()
Returns the Date object's standard date-time string format string
toTimeString()
Returns the string that returns the time part of the Date object
toJSON()
Returns a date string that conforms to JSON format, which is exactly the same as the return result of the toISOString method
console.log(new Date('2016-7-12').toString());//Tue Jul 12 2016 00:00:00 GMT+0800 (China Standard Time)console.log(new Date('2016-7-12').toUTCString());//Mon, 11 Jul 2016 16:00:00 GMTconsole.log(new Date('2016-7-12').toISOSString());//2016-07-11T16:00:00.000Zconsole.log(new Date('2016-7-12').toDateString());//Tue Jul 12 2016console.log(new Date('2016-7-12').toTimeString());//00:00:00 GMT+0800 (China Standard Time)console.log(new Date('2016-7-12').toJSON());//2016-07-11T16:00:00.000ZtoLocaleString()
Localized conversion of toString() method
toLocaleTimeString()
Localized conversion of toTimeString() method
toLocaleDateString()
Localized conversion of toDateString() method
console.log(new Date('2016-7-12').toString());//Tue Jul 12 2016 00:00:00 GMT+0800 (China Standard Time)console.log(new Date('2016-7-12').toLocaleString());//2016/7/12 12:00:00 Console.log(new Date('2016-7-12').toDateString());//Tue Jul 12 2016console.log(new Date('2016-7-12').toLocaleDateString());//2016/7/12console.log(new Date('2016-7-12').toTimeString());//00:00:00 GMT+0800 (China Standard Time)console.log(new Date('2016-7-12').toLocaleTimeString());//12:00:00 am【get class】
The Date object provides a series of get class methods to obtain the value of a certain aspect of the instance object.
Before introducing the get class method, we must first introduce the valueOf() method
valueOf()
Returns the number of milliseconds from 0:00 on January 1, 1970
Therefore, it is convenient to use the comparison operator to compare date values
var date1 = new Date(2007,0,1);var date2 = new Date(2007,1,1);console.log(date1 > date2);//falseconsole.log(date1 < date2);//true
getTime()
Returns the number of milliseconds from 0:00 on January 1, 1970, same as valueOf()
Before ECMAScript5, you can use the getTime() method to implement Date.now()
Date.now = function(){ return (new Date()).getTime() }getTimezoneOffset()
Returns the time zone difference between the current time and UTC, expressed in minutes (8*60=480 minutes). The return result takes into account daylight saving time factors.
console.log(new Date('2016-7-12').valueOf());//1468252800000console.log(new Date('2016-7-12').getTime());//1468252800000console.log(new Date('2016-7-12').getTimezoneOffset());//-480getYear()
Returns the number of years from 1900 (outdated)
get[UTC]FullYear()
Return year (4 digits)
get[UTC]Month()
Return to month (0-11)
get[UTC]Date()
Return to what day (1-31)
get[UTC]Day()
Return to the day of the week (0-6)
get[UTC]Hours()
Return hour value (0-23)
get[UTC]Minutes()
Returns the minute value (0-59)
get[UTC]Seconds()
Returns the second value (0-59)
get[UTC]Milliseconds()
Return millisecond value (0-999)
[Note] UTC time is set by the standard date and time format string and has parameter settings in the form of pre-0.
console.log(new Date('2016-07-12T10:00').getYear());//116console.log(new Date('2016-07-12T10:00').getFullYear());//2016console.log(new Date('2016-07-12T10:00').getUTCFullYear());//2016console.log(new Date('2016-07-12T10:00').getMonth());//6console.log(new Date('2016-07-12T10:00').getUTCMonth());//6console.log(new Date('2016-07-12T10:00').getDate());//12console.log(new Date('2016-07-12T10:00').getUTCDate());//2console.log(new Date('2016-07-12T10:00').getUTCDay());//2console.log(new Date('2016-07-12T10:00').getUTCDay());//2console.log(new Date('2016-07-12T10:00').getHours());//18console.log(new Date('2016-07-12T10:00').getUTCHours());//10console.log(new Date('2016-07-12T10:00').getMinutes());//0console.log(new Date('2016-07-12T10:00').getUTCMinutes());//0console.log(new Date('2016-07-12T10:00').getSeconds());//0console.log(new Date('2016-07-12T10:00').getUTCSeconds());//0console.log(new Date('2016-07-12T10:00').getMilliseconds());//0console.log(new Date('2016-07-12T10:00').getUTCMilliseconds());//0//The current time is 16:35console.log(new Date().getHours());//16console.log(new Date().getUTCHours());//8
【set class】
The Date object provides a series of set class methods to set various aspects of the instance object.
The set method basically corresponds to the get method. The set method passes in a parameter similar to Date.UTC() and returns the number of internal milliseconds of the adjusted date
[Note] Only get it in the week, not set
setTime()
Use millisecond format to set the value of a Date object
var d = new Date('2016-07-12T10:00');console.log(d.setTime(86400000),d);//86400000 Fri Jan 02 1970 08:00:00 GMT+0800 (China Standard Time)setYear()
Set Year (outdated)
var d = new Date('2016-07-12T10:00');console.log(d.setYear(2000),d,d.getYear());//963396000000 Wed Jul 12 2000 18:00:00 GMT+0800 (China Standard Time) 100set[UTC]FullYear()
Set year (4 digits), and optional month and date values
set[UTC]Month()
Set month (0-11), and optional date values
set[UTC]Date()
Set the day (1-31)
var d = new Date('2016-07-12T10:00');console.log(d.setFullYear(2015,1,1),d.getFullYear());//1422784800000 2015console.log(d.setMonth(2),d.getMonth());//1425204000000 2console.log(d.setDate(20),d.getDate());//1426845600000 20console.log(d.toLocaleString());//2015/3/20 6:00:00 pmset[UTC]Hours()
Set hour values (0-23), as well as optional minute values, second values and millisecond values
set[UTC]Minutes()
Set the minute value (0-59), as well as optional second value and millisecond value
set[UTC]Seconds()
Set the second value (0-59), and optional millisecond value
set[UTC]Milliseconds()
Set millisecond value (0-999)
var d = new Date('2016-07-12T10:20:30');console.log(d.setHours(1,2,3),d.getHours());//1468256523000 1console.log(d.setMinutes(2,3),d.getMinutes());//1468256523000 2console.log(d.setSeconds(3),d.getSeconds());//1468256523000 3console.log(d.toLocaleTimeString())//1:02:03 am var d = new Date('2016-07-12T10:20:30');console.log(d.setUTCHours(1,2,3),d.getHours());//1468285323000 9console.log(d.setUTCMinutes(2,3),d.getMinutes());//1468285323000 2console.log(d.setUTCSeconds(3),d.getSeconds());//1468285323000 3console.log(d.toLocaleTimeString())//9:02:03 amThe above article on JavaScript type system - a comprehensive understanding of the date Date object is all the content I have shared with you. I hope you can give you a reference and I hope you can support Wulin.com more.