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)
To use Date methods:
dateObjectName.methodName(parameters)Exceptions: The Date object's parse and UTC methods are static methods that you use as follows:
Date.UTC(parameters) Date.parse(parameters)
Event handlers
None. Built-in objects do not have event handlers.
Examples
The following examples show several ways to assign dates:
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.
Syntax
1. checkboxName.defaultChecked
2. radioName[index].defaultChecked
Parameters
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
Description
If a 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.
Examples
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.
Syntax
selectName.options[index].defaultSelected
Parameters
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 (see select object)
Description
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.
Examples
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.
Syntax
windowReference.defaultStatus
Parameters
windowReference is a valid way of referring to a window, as described in the window object.
Description
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.
Examples
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.
Syntax
1. passwordName.defaultValue
2. textName.defaultValue
3. textareaName.defaultValue
Parameters
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 object, text object, textarea object
Description
The initial value of defaultValue differs for each object:
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.
Examples
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 HTML output to the user.
HTML syntax
To define a document object, use standard HTML syntax:
<BODY
BACKGROUND="backgroundImage"
BGCOLOR="backgroundColor"
TEXT="foregroundColor"
LINK="unfollowedLinkColor"
ALINK="activatedLinkColor"
VLINK="followedLinkColor"
[onLoad="handlerText"]
[onUnload="handlerText"]>
</BODY>
HTML attributes
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".
Syntax
To use a document object's properties and methods:
1. document.propertyName
2. document.methodName(parameters)
Parameters
propertyName is one of the properties listed below.
methodName is one of the methods listed below.
Property of
window object
Description
An HTML document consists of HEAD and BODY tags. The HEAD tag 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 HTML 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
The document object has the following properties:
The following objects are also properties of the document object:
Methods
The document object has the following 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.
Examples
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.html, which defines the frames, contains the following code:
<HTML>
<HEAD>
<TITLE>Document object example</TITLE>
</HEAD>
<FRAMESET COLS="30%,70%">
<FRAME SRC="doc1.html" NAME="frame1">
<FRAME SRC="doc2.html" NAME="frame2">
</FRAMESET>
</HTML>
doc1.html, which defines the content for the first frame, contains the following code:
<HTML>
<SCRIPT>
</SCRIPT>
<BODY
BGCOLOR="antiquewhite"
TEXT="darkviolet"
LINK="fuchsia"
ALINK="forestgreen"
VLINK="navy">
<P><B>Some links</B>
<LI><A HREF="doc2.html#numbers" TARGET="frame2">Numbers</A>
<LI><A HREF="doc2.html#colors" TARGET="frame2">Colors</A>
<LI><A HREF="doc2.html#musicTypes" TARGET="frame2">Music types</A>
<LI><A HREF="doc2.html#countries" TARGET="frame2">Countries</A>
</BODY>
</HTML>
doc2.html, which defines the content for the second frame, contains the following code:
<HTML>
<SCRIPT>
</SCRIPT>
<BODY
BGCOLOR="oldlace" onLoad="alert('Hello, World.')"
TEXT="navy">
<P><A NAME="numbers"><B>Some numbers</B></A>
<UL><LI>one
<LI>two
<LI>three
<LI>four</UL>
<P><A NAME="colors"><B>Some colors</B></A>
<UL><LI>red
<LI>orange
<LI>yellow
<LI>green</UL>
<P><A NAME="musicTypes"><B>Some music types</B></A>
<UL><LI>R&B
<LI>Jazz
<LI>Soul
<LI>Reggae</UL>
<P><A NAME="countries"><B>Some countries</B></A>
<UL><LI>Afghanistan
<LI>Brazil
<LI>Canada
<LI>Finland</UL>
</BODY>
</HTML>
See also
frame object, window object
E
Property. Euler's constant and the base of natural logarithms, approximately 2.718.
Syntax
Math.E
Property of
Math
Description
Because E is a constant, it is a read-only property of Math.
Examples
The following function returns Euler's constant:
function getEuler() {
return Math.E
}
See also
LN2, LN10, LOG2E, LOG10E, PI, SQRT1_2, SQRT2 properties
elements array
Property. An array of objects corresponding to form elements (such as checkbox, radio, and text objects) in source order.
Syntax
1. formName.elements[index]
2. formName.elements.length
Parameters
formName is either the name of a form or an element in the forms array.
index is an integer representing an object on a form.
Property of
form
Description
You can reference a form's elements in your code by using the elements array. This array contains an entry for each object (button, checkbox, hidden, password, radio, reset, select, submit, text, or textarea object) in a form in source order. For example, if a form has a text field and two checkboxes, these elements are reflected as formName.elements[0], formName.elements[1], and formName.elements[2].
Although you can also reference a form's elements by using the element's name (from the NAME attribute), the elements array provides a way to reference form objects programmatically without using their names. For example, if the first object on the userInfo form is the userName text object, you can evaluate it in either of the following ways:
userInfo.userName.value
userInfo.elements[0].value
To obtain the number of elements on a form, use the length property: formName.elements.length. Each radio button in a radio object appears as a separate element in the elements array.
Elements in the elements array are read-only. For example, the statement formName.elements[0]="music" has no effect.
The value of each element in the elements array is the full HTML statement for the object.
Properties
The elements array has one property, length, that reflects the number of elements in the form.
:Examples
See the examples for the name property.
elements property
Property. An array of objects corresponding to form elements (such as checkbox, radio, and text objects) in source order. See the elements array for information.
encoding
Property. A string specifying the MIME encoding of the form.
Syntax
formName.encoding
Parameters
formName is either the name of a form or an element in the forms array.
Property of
form
Description
The encoding property initially reflects the ENCTYPE attribute of the FORM tag; however, setting encoding overrides the ENCTYPE attribute.
You can set the encoding property at any time.
Examples
The following function returns the value of the musicForm encoding property:
function getEncoding() {
return document.musicForm.encoding
}
See also
action, method, target properties; form object
escape
Function. Returns the ASCII encoding of an argument in the ISO Latin-1 character set.
Syntax
escape("string")
Parameters
string is a nonalphanumeric string in the ISO Latin-1 character set, or a property of an existing object.
Description
The value returned by the escape function is a string of the form "%xx," where xx is the ASCII encoding of a character in the argument. If you pass the escape function an alphanumeric character, the escape function returns the same character. escape is a top-level function not associated with any object.
Examples
The following example returns "%26":
escape("&")
The following example returns "%21%23":
escape("!#")
See also
unescape function
eval
Function. The eval function evaluates a string and returns a value.
Syntax
eval(string)
Parameters
string is any string representing a JavaScript expression, statement, or sequence of statements. The expression can include variables and properties of existing objects.
Description
The eval function is a built-in JavaScript function. It is not a method associated with any object, but is part of the language itself.
The argument of the eval function is a string. If the string represents an expression, eval evaluates the expression. If the argument represents one or more JavaScript statements, eval performs the statements. Do not call eval to evaluate an arithmetic expression; JavaScript evaluates arithmetic expressions automatically.
If you construct an arithmetic expression as a string, you can use eval to evaluate it at a later time. For example, suppose you have a variable x. You can postpone evaluation of an expression involving x by assigning the string value of the expression, say "3 * x + 2", to a variable, and then calling eval at a later point in your script.
Examples
The following examples display output using document.write. In LiveWire, you can display the same output by calling the write function instead of using document.write.
Example 1. Both of the write statements below display 42. The first evaluates the string "x + y + 1," and the second evaluates the string "42."
var x = 2
var y = 39
var z = "42"
document.write(eval("x + y + 1"), "<BR>")
document.write(eval(z), "<BR>")
Example 2. In the following example, the getFieldName(n) function returns the name of the nth form element as a string. The first statement assigns the string value of the third form element to the variable field. The second statement uses eval to display the value of the form element.
var field = getFieldName(3)
document.write("The field named ", field, " has value of ", eval(field + ".value"))
Example 3. The following example uses eval to evaluate the string str. This string consists of JavaScript statements that open an Alert dialog box and assigns z a value of forty-two if x is five, and assigns zero to z otherwise. When the second statement is executed, eval will cause these statements to be performed, and it will also evaluate the set of statements and return the value that is assigned to z.
var str = "if (x == 5) {alert('z is 42'); z = 42;} else z = 0; "
document.write("<P>z is ", eval(str))
Example 4. In the following example, the setValue function uses eval to assign the value of the variable newValue to the text field textObject:
function setValue (textObject, newValue) {
eval ("document.forms[0]." + textObject + ".value") = newValue
}
exp
Method. Returns enumber, where number is the argument, and e is Euler's constant, the base of the natural logarithms.
Syntax
Math.exp(number)
Parameters
number is any numeric expression or a property of an existing object.
Method of
Math
Examples
The following function returns the exp value of the variable x:
function getExp(x) {
return Math.exp(x)
}
If you pass getExp the value 1, it returns 2.718281828459045.
See also
log, pow methods