javascript手冊-d

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

Methods

Event handlers

例子

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

checkbox, radio

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

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

      }

   }

}

<select NAME="musicType">

   <option SELECTED> R&B

   <option> Jazz

   <option> Blues

   <option> New Age

</select>

See also

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

window

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"

}

Netscape

See also

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

password, text, textarea

描述

The initial value of defaultValue differs for each object:

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 + "
")

   msgWindow.document.write("password.defaultValue is " +

      document.surfCity.passwordObj.defaultValue + "
")

   msgWindow.document.write("text.defaultValue is " +

      document.surfCity.textObj.defaultValue + "
")

   msgWindow.document.write("textarea.defaultValue is " +

      document.surfCity.textareaObj.defaultValue + "
")

   msgWindow.document.close()

}

See also

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=""

   BGCOLOR="backgroundColor"

   TEXT="foregroundColor"

   LINK="unfollowedLinkColor"

   ALINK="activatedLinkColor"

   VLINK="followedLinkColor"

   [onLoad="handlerText"]

   [onUnload="handlerText"]>

</body>

To use a document object's properties and methods:

1. document.propertyName

2. document.methodName(parameters)

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

DOC1.htm, which defines the content for the first frame, contains the following code:

DOC2.htm, which defines the content for the second frame, contains the following code:

See also