Date object
Lets you work with dates and times.
语法
To create a Date object: 1. dateObjectName = new Date()
2. dateObjectName = new Date("month day, year hours:minutes:seconds")
3. dateObjectName = new Date(year, month, day)
4. dateObjectName = new Date(year, month, day, hours, minutes, seconds)
dateObjectName is either the name of a new object or a property of an existing object.
month, day, year, hours, minutes, and seconds are string values for form 2 of the 语法. For forms 3 and 4, they are integer values.
To use Date methods: dateObjectName.methodName(parameters)
dateObjectName is either the name of an existing Date object or a property of an existing object..
methodName is one of the methods listed below.
Exceptions: The Date object's parse and UTC methods are static methods that you use as follows: Date.UTC(parameters)
Date.parse(parameters)
Property of
None.
描述
The Date object is a built-in JavaScript object.
Form 1 of the 语法 creates today's date and time. If you omit hours, minutes, or seconds from form 2 or 4 of the 语法, the value will be set to zero.
The way JavaScript handles dates is very similar to the way Java handles dates: both languages have many of the same date methods, and both store dates internally as the number of milliseconds since January 1, 1970 00:00:00. Dates prior to 1970 are not allowed.
Properties
None.
Methods
Event handlers
None. Built-in objects do not have event handlers.
例子
today = new Date()
birthday = new Date("December 17, 1995 03:24:00")
birthday = new Date(95,12,17)
birthday = new Date(95,12,17,3,24,0)
defaultChecked property
A Boolean value indicating the default selection state of a checkbox or radio button.
语法1. checkboxName.defaultChecked
2. radioName[index].defaultChecked
checkboxName is either the value of the NAME attribute of a checkbox object or an element in the elements array.
radioName is the value of the NAME attribute of a radio object.
index is an integer representing a radio button in a radio object.
Property of
描述
If an checkbox or radio button is selected by default, the value of the defaultChecked property is true; otherwise, it is false. defaultChecked initially reflects whether the CHECKED attribute is used within an <INPUT> tag; however, setting defaultChecked overrides the CHECKED attribute.
You can set the defaultChecked property at any time. The display of the checkbox or radio button does not update when you set the defaultChecked property, only when you set the checked property.
例子
The following example resets an array of radio buttons called musicType on the musicForm form to the default selection state. function radioResetter() {
var i=""
for (i in document.musicForm.musicType) {
if (document.musicForm.musicType[i].defaultChecked==true) {
document.musicForm.musicType[i].checked=true
}
}
}
See also
checked property
defaultSelected property
A Boolean value indicating the default selection state of an option in a select object.
语法selectName.options[index].defaultSelected
selectName is either the value of the NAME attribute of a select object or an element in the elements array.
index is an integer representing an option in a select object.
Property of
options array
描述
If an option in a select object is selected by default, the value of the defaultSelected property is true; otherwise, it is false. defaultSelected initially reflects whether the SELECTED attribute is used within an <OPTION> tag; however, setting defaultSelected overrides the SELECTED attribute.
You can set the defaultSelected property at any time. The display of the select object does not update when you set the defaultSelected property, only when you set the selected or selectedIndex properties.
A select object created without the MULTIPLE attribute can have only one option selected by default. When you set defaultSelected in such an object, any previous default selections, including defaults set with the SELECTED attribute, are cleared. If you set defaultSelected in a select object created with the MULTIPLE attribute, previous default selections are not affected.
例子
In the following example, the restoreDefault() function returns the musicType select object to its default state. The for loop uses the options array to evaluate every option in the select object. The if statement sets the selected property if defaultSelected is true. function restoreDefault() {
for (var i = 0; i < document.musicForm.musicType.length; i++) {
if (document.musicForm.musicType.options[i].defaultSelected == true) {
document.musicForm.musicType.options[i].selected=true
}
}
}
The previous example assumes that the select object is similar to the following: <SELECT NAME="musicType">
<OPTION SELECTED> R&B
<OPTION> Jazz
<OPTION> Blues
<OPTION> New Age
</SELECT>
See also
index, selected, selectedIndex properties
defaultStatus property
The default message displayed in the status bar at the bottom of the window.
语法windowReference.defaultStatus
windowReference is a valid way of referring to a window, as described in the window object.
Property of
描述
The defaultStatus message appears when nothing else is in the status bar. Do not confuse the defaultStatus property with the status property. The status property reflects a priority or transient message in the status bar, such as the message that appears when a mouseOver event occurs over an anchor.
You can set the defaultStatus property at any time. You must return true if you want to set the defaultStatus property in the onMouseOver event handler.
例子
In the following example, the statusSetter() function sets both the status and defaultStatus properties in an onMouseOver event handler: function statusSetter() {
window.defaultStatus = "Click the link for the Netscape home page"
window.status = "Netscape home page"
}
<A HREF="http://www.netscape.com"
onMouseOver = "statusSetter(); return true">Netscape</A>
In the previous example, notice that the onMouseOver event handler returns a value of true. You must return true to set status or defaultStatus in an event handler.
See also
status property
defaultValue property
A string indicating the default value of a password, text, or textarea object.
语法1. passwordName.defaultValue
2. textName.defaultValue
3. textareaName.defaultValue
passwordName is either the value of the NAME attribute of a password object or an element in the elements array.
textName is either the value of the NAME attribute of a text object or an element in the elements array.
textareaName is either the value of the NAME attribute of a textarea object or an element in the elements array.
Property of
描述
The initial value of defaultValue differs for each object:
For text objects, it initially reflects the value of the VALUE attribute.
For textarea objects, it initially reflects the value specified between the <TEXTAREA> and </TEXTAREA> tags.
For password objects, it initially is null (for security reasons), regardless of the value of the VALUE attribute.
Setting defaultValue programatically overrides the initial setting. If you programatically set defaultValue for the password object and then evaluate it, JavaScript returns the current value.
You can set the defaultValue property at any time. The display of the related object does not update when you set the defaultValue property, only when you set the value property.
例子
The following function evaluates the defaultValue property of objects on the surfCity form and displays the values in the msgWindow window: function defaultGetter() {
msgWindow=window.open("")
msgWindow.document.write("hidden.defaultValue is " +
document.surfCity.hiddenObj.defaultValue + "<BR>")
msgWindow.document.write("password.defaultValue is " +
document.surfCity.passwordObj.defaultValue + "<BR>")
msgWindow.document.write("text.defaultValue is " +
document.surfCity.textObj.defaultValue + "<BR>")
msgWindow.document.write("textarea.defaultValue is " +
document.surfCity.textareaObj.defaultValue + "<BR>")
msgWindow.document.close()
}
See also
value property
document object
Contains information on the current document, and provides methods for displaying htm output to the user.
语法
To define a document object, use standard htm 语法: <BODY
BACKGROUND="backgroundImage"
BGCOLOR="backgroundColor"
TEXT="foregroundColor"
LINK="unfollowedLinkColor"
ALINK="activatedLinkColor"
VLINK="followedLinkColor"
[onLoad="handlerText"]
[onUnload="handlerText"]>
</BODY>
BACKGROUND specifies an image that fills the background of the document.
BGCOLOR, TEXT, LINK, ALINK, and VLINK are color specifications expressed as a hexadecimal RGB triplet (in the format "rrggbb" or "#rrggbb") or as one of the string literals listed in Color Values.
To use a document object's properties and methods: 1. document.propertyName
2. document.methodName(parameters)
propertyName is one of the properties listed below.
methodName is one of the methods listed below.
Property of
描述
An htm document consists of a <HEAD> and <BODY> tag. The <HEAD> includes information on the document's title and base (the absolute URL base to be used for relative URL links in the document). The <BODY> tag encloses the body of a document, which is defined by the current URL. The entire body of the document (all other htm elements for the document) goes within the <BODY> tag.
You can load a new document by using the location object.
You can reference the anchors, forms, and links of a document by using the anchors, forms, and links arrays. These arrays contain an entry for each anchor, form, or link in a document.
Properties
alinkColor reflects the ALINK attribute
anchors is an array reflecting all the anchors in a document
bgColor reflects the BGCOLOR attribute
cookie specifies a cookie
fgColor reflects the TEXT attribute
forms is an array reflecting all the forms in a document
lastModified reflects the date a document was last modified
linkColor reflects the LINK attribute
links is an array reflecting all the links in a document
location reflects the complete URL of a document
referrer reflects the URL of the calling document
title reflects the contents of the <TITLE> tag
vlinkColor reflects the VLINK attribute
The following objects are also properties of the document object:
Methods
Event handlers
None. The onLoad and onUnload event handlers are specified in the <BODY> tag but are actually event handlers for the window object.
例子
The following example creates two frames, each with one document. The document in the first frame contains links to anchors in the document of the second frame. Each document defines its colors.
DOC0.htm, which defines the frames, contains the following code:
Document object example
DOC1.htm, which defines the content for the first frame, contains the following code:
Some links
DOC2.htm, which defines the content for the second frame, contains the following code:
Some numbers
one
two
three
four
five
six
seven
eight
nine
Some colors
red
orange
yellow
green
blue
purple
brown
black
Some music types
R&B
Jazz
Soul
Reggae
Rock
Country
Classical
Opera
Some countries
Afghanistan
Brazil
Canada
Finland
India
Italy
Japan
Kenya
Mexico
Nigeria
See also
