Shulou(Shulou.com)05/31 Report--

I hope you can read it carefully and be able to achieve something!

Next, we will explain the second common built-in object in JS-- the Date object.

Date object is different from Math object, Math object is not a constructor and can be used directly, while Date object is a constructor, so we must instantiate the object, that is, new before we can use it. Date object is mostly used to deal with time and date problems in development.

Date object instantiation: var date=new Date ()

Date objects can be instantiated with or without parameters. The output without parameters is the standard time of the current system at that time. If there are parameters, we can output the time we want to display.

One: instantiation without parameters

No parameters are instantiated to show the time and date of the current system.

Var date=new Date (); / / has no parameter console.log (date); / / outputs the current time

Second, instantiation of parameters

There are two types of parameter instantiation, which are numeric type and string type. The following examples are given to illustrate the two types.

1. Instantiation of numeric parameters:

Var date=new Date (2021 and 1); / / numeric parameter console.log (date)

You can see that the parameter we entered is January, but the output is Feb (February), and the digital output will be one month larger than the month we entered.

two。 Instantiation of string parameters:

Var date=new Date ('2021-1-18 12 date 56); / / string parameter console.log (date)

The parameter is January, and the result of the output is January, so there are more string parameters than numeric ones.

Three: format the year, month and day

GetFullYear () outputs the current year

GetMonth () outputs the current month (note that the output month is 1 less than the actual month, and the output real month should be increased by 1)

GetDate () output the current number

GetDay () outputs the current day of the week (corresponding numbers from Monday to Sunday: 1 2 3 4 5 60)

Var Date=new Date (); console.log (Date.getFullYear ()); / / output the current year console.log (Date.getMonth () + 1); / / the output result is the previous month of the current month, and you need to manually add 1 to return the current month console.log (Date.getDate ()); / / output the current number of console.log (Date.getDay ()); / / output the current day of the week

If you want the output to be Tuesday, January 18, 2021, you can do the following

(because the day of the week can only return one number, but according to custom we want to return 'day of the week', so we take the returned number as an index and put it in an array from Sunday to Saturday. Because Sunday returns 0, so put Sunday in the first position of the array, which corresponds to the 0 index.)

Var arr= [Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday]; var Date=new Date (); var year=Date.getFullYear (); var month=Date.getMonth () + 1; var date=Date.getDate (); var day=Date.getDay (); console.log (year + year + month + month + date + day + arr [day])

Four: minutes and seconds when formatting

Similar to the method of formatting year, month and day above

GetHours () outputs the current hour

GetMinutes () outputs the current minute

GetSeconds () output current second

Var Date=new Date (); console.log (Date.getHours ()); / / output current hour console.log (Date.getMinutes ()); / / output current minute console.log (Date.getSeconds ()); / / output current second

Output continuous format minutes and seconds:

It is encapsulated in the function, and the number less than 10 is added to 0 by using the ternary operator, which is in line with the usual habit of looking at time.

Function time () {var time=new Date (); var h=time.getHours (); h = h

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