Date() constructor
Creates a JavaScript Date
instance that represents a single moment in time in a platform-independent format. Date
objects contain a Number
that represents milliseconds since 1 January 1970 UTC.
尝试一下
Syntax
new Date() new Date(value) new Date(dateString) new Date(year, monthIndex [, day [, hours [, minutes [, seconds [, milliseconds]]]]])
备注: The only correct way to instantiate a new Date
object is by using the new
operator. If you simply call the Date
object directly, such as now = Date()
, the returned value is a string rather than a Date
object.
Parameters
There are four basic forms for the Date()
constructor:
-
No parameters
When no parameters are provided, the newly-createdDate
object represents the current date and time as of the time of instantiation. -
Time value or timestamp number
value
-
An integer value representing the number of milliseconds since January 1, 1970, 00:00:00 UTC (the ECMAScript epoch, equivalent to the UNIX epoch), with leap seconds ignored. Keep in mind that most UNIX Timestamp functions are only accurate to the nearest second.
-
Timestamp string
dateString
-
A string value representing a date, specified in a format recognized by the
Date.parse()
method. (These formats are IETF-compliant RFC 2822 timestamps, and also strings in a version of ISO8601.)备注: Parsing of date strings with the
Date
constructor (andDate.parse()
, which works the same way) is strongly discouraged due to browser differences and inconsistencies.- Support for RFC 2822 format strings is by convention only.
- Support for ISO 8601 formats differs in that date-only strings (e.g.
"1970-01-01"
) are treated as UTC, not local.
-
Individual date and time component values
Given at least a year and month, this form ofDate()
returns aDate
object whose component values (year, month, day, hour, minute, second, and millisecond) all come from the following parameters. Any missing fields are given the lowest possible value (1
forday
and0
for every other component).year
-
Integer value representing the year.
Values from
0
to99
map to the years1900
to1999
. All other values are the actual year. See the example below. monthIndex
-
Integer value representing the month, beginning with
0
for January to11
for December. day
可选-
Integer value representing the day of the month. The default is
1
. hours
可选-
Integer value representing the hour of the day. The default is
0
(midnight). minutes
可选-
Integer value representing the minute segment of a time. The default is
0
minutes past the hour. seconds
可选-
Integer value representing the second segment of a time. The default is
0
seconds past the minute. milliseconds
可选-
Integer value representing the millisecond segment of a time. The default is
0
milliseconds past the second.
Specifications
Specification |
---|
ECMAScript Language Specification # sec-date-constructor |
Browser compatibility
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