A string beginning with a hash mark (#) that specifies an anchor name in the URL.
1. links[index].hash 2. location.hash
index is an integer representing a link object.
The hash property specifies a portion of the URL.
You can set the hash property at any time, although it is safer to set the href property to change a location. If the hash that you specify cannot be found in the current location, you will get an error.
See RFC 1738 for complete information about the hash.
See the 例子 for the anchor object and the href property.
A text object that is suppressed from form display on an htm form. A hidden object is used for passing name/value pairs when a form submits.
To define a hidden object:
<INPUT TYPE="hidden" NAME="hiddenName" [VALUE="textValue"]>NAME="hiddenName" specifies the name of the hidden object. You can access this value using the name property.
To use a hidden object's properties:
1. hiddenName.propertyName 2. formName.elements[index].propertyNamehiddenName is the value of the NAME attribute of a hidden object.
A hidden object is a form element and must be defined within a <FORM> tag.
A hidden object cannot be seen or modified by a user, but you can programatically change the value of the object by changing its value property. You can use hidden objects for client/server communication.
Contains information on the URLs that the client has visited within a window. This information is stored in a history list, and is accessible through the Navigator's Go menu.
To use a history object:
1. history.propertyName 2. history.methodName(parameters)propertyName is one of the properties listed below.
The history object is a linked list of URLs the user has visited, as shown in the Navigator's Go menu.
Example 1. The following example goes to the URL the user visited three clicks ago in the current window.
Example 2. You can use the history object with a specific window or frame. The following example causes window2 to go back one item in its window (or session) history:
Example 3. The following example causes the second frame in a frameset to go back one item:
Example 4. The following example causes the frame named frame1 in a frameset to go back one item:
Example 5. The following example causes the frame named frame2 in window2 to go back one item:
A string specifying the hostname:port portion of the URL.
1. links[index].host 2. location.host
index is an integer representing a link object.
The host property specifies a portion of the URL. The host property is the concatenation of the hostname and port properties, separated by a colon. When the port property is null, the host property is the same as the hostname property.
You can set the host property at any time, although it is safer to set the href property to change a location. If the host that you specify cannot be found in the current location, you will get an error.
See Section 3.1 of RFC 1738 for complete information about the hostname and port.
See the 例子 for the href property.
A string specifying the host and domain name, or IP address, of a network host.
1. links[index].hostname 2. location.hostname
index is an integer representing a link object.
The hostname property specifies a portion of the URL. The hostname property is a substring of the host property. The host property is the concatenation of the hostname and port properties, separated by a colon. When the port property is null, the host property is the same as the hostname property.
You can set the hostname property at any time, although it is safer to set the href property to change a location. If the hostname that you specify cannot be found in the current location, you will get an error.
See Section 3.1 of RFC 1738 for complete information about the hostname.
See the 例子 for the href property.
A string specifying the entire URL.
1. links[index].href 2. location.href
index is an integer representing a link object.
The href property specifies the entire URL. Other location object properties are substrings of the href property. You can set the href property at any time.
Omitting a property name from the location object is equivalent to specifying location.href. For example, the following two statements are equivalent and set the URL of the current window to the Netscape home page:
See RFC 1738 for complete information about the URL.
In the following example, the window.open statement creates a window called newWindow and loads the specified URL into it. The document.write statements display all the properties of newWindow.location in a window called msgWindow.
newWindow=window.open
("http://home.netscape.com/comprod/products/navigator/
version_2.0/script/script_info/objects.htm#checkbox_object")
msgWindow.document.write("newWindow.location.href = " +
newWindow.location.href + "<P>")
msgWindow.document.write("newWindow.location.protocol = " +
newWindow.location.protocol + "<P>")
msgWindow.document.write("newWindow.location.host = " +
newWindow.location.host + "<P>")
msgWindow.document.write("newWindow.location.hostName = " +
newWindow.location.hostName + "<P>")
msgWindow.document.write("newWindow.location.port = " +
newWindow.location.port + "<P>")
msgWindow.document.write("newWindow.location.pathname = " +
newWindow.location.pathname + "<P>")
msgWindow.document.write("newWindow.location.search = " +
newWindow.location.search + "<P>")
msgWindow.document.write("newWindow.location.hash = " +
newWindow.location.hash + "<P>")
msgWindow.document.close()
The previous example displays output such as the following:
newWindow.location.href = http://home.netscape.com/comprod/products/navigator/ version_2.0/script/script_info/objects.htm#checkbox_object newWindow.location.protocol = http: newWindow.location.host = home.netscape.com newWindow.location.hostName = home.netscape.com newWindow.location.port = newWindow.location.pathname = /comprod/products/navigator/version_2.0/script/ script_info/objects.htm newWindow.location.search = newWindow.location.hash = #checkbox_object
An integer representing the index of an option in a select object.
selectName.options[indexValue].index
selectName is either the value of the NAME attribute of a select object or an element in the elements array.
indexValue is an integer representing an option in a select object.
options array
The number identifying the position of the option in the selection, starting from zero.
Returns the index within the calling string object of the first occurrence of the specified value, starting the search at fromIndex.
stringName.indexOf(searchValue, [fromIndex])
stringName is any string or a property of an existing object.
searchValue is a string or a property of an existing object, representing the value to search for.
fromIndex is the location within the calling string to start the search from. It can be any integer from 0 to stringName.length - 1 or a property of an existing object.
Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character is stringName.length - 1.
If you do not specify a value for fromIndex, JavaScript assumes 0 by default. If searchValue is not found, JavaScript returns -1.
var anyString="Brave new world"
//Displays 8
document.write("<P>The index of the first w from the beginning is " +
anyString.indexOf("w"))
//Displays 10
document.write("<P>The index of the first w from the end is " +
anyString.lastIndexOf("w"))
//Displays 6
document.write("<P>The index of 'new' from the beginning is " +
anyString.indexOf("new"))
//Displays 6
document.write("<P>The index of 'new' from the end is " +
anyString.lastIndexOf("new"))
On Unix platforms, evaluates an argument to determine if it is "NaN" (not a number).
isNaN(testValue)
testValue is the value you want to evaluate.
The isNaN function is a built-in JavaScript function. It is not a method associated with any object, but is part of the language itself. isNaN is available on Unix platforms only.
On all platforms except Windows, the parseFloat and parseInt functions return "NaN" when they evaluate a value that is not a number. The "NaN" value is not a number in any radix. You can call the isNaN function to determine if the result of parseFloat or parseInt is "NaN". If "NaN" is passed on to arithmetic operations, the operation results will also be "NaN".
The isNaN function returns true or false.
The following example evaluates floatValue to determine if it is a number, then calls a procedure accordingly.
floatValue=parseFloat(toFloat)
if isNaN(floatValue) {
notFloat()
} else {
isFloat()
}
Causes a string to be italicized as if it were in an <I> tag.
stringName.italics()
stringName is any string or a property of an existing object.
Use the italics method with the write or writeln methods to format and display a string in a document.
var worldString="Hello, world"
document.write(worldString.blink())
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())
The previous example produces the same output as the following htm:
<BLINK>Hello, world</BLINK> <P><B>Hello, world</B> <P><I>Hello, world</I> <P><STRIKE>Hello, world</STRIKE>
Returns the index within the calling string object of the last occurrence of the specified value. The calling string is searched backwards, starting at fromIndex.
stringName.lastIndexOf(searchValue, [fromIndex])
stringName is any string or a property of an existing object.
searchValue is a string or a property of an existing object, representing the value to search for.
fromIndex is the location within the calling string to start the search from. It can be any integer from 0 to stringName.length - 1 or a property of an existing object.
Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character is stringName.length - 1.
If you do not specify a value for fromIndex, JavaScript assumes stringName.length - 1 (the end of the string) by default. If searchValue is not found, JavaScript returns -1.
var anyString="Brave new world"
//Displays 8
document.write("<P>The index of the first w from the beginning is " +
anyString.indexOf("w"))
//Displays 10
document.write("<P>The index of the first w from the end is " +
anyString.lastIndexOf("w"))
//Displays 6
document.write("<P>The index of 'new' from the beginning is " +
anyString.indexOf("new"))
//Displays 6
document.write("<P>The index of 'new' from the end is " +
anyString.lastIndexOf("new"))
A string representing the date that a document was last modified.
document.lastModified
lastModified is a read-only property.
In the following example, the lastModified property is used in a <SCRIPT> tag at the end of an htm file to display the modification date of the page:
document.write("This page updated on " + document.lastModified)
An integer that specifies a length-related feature of the calling object or array.
When used with objects:
1. formName.length 2. frameReference.length 3. history.length 4. radioName.length 5. selectName.length 6. stringName.length 7. windowReference.length
When used with array properties:
8. anchors.length 9. elements.length 10. forms.length 11. frameReference.frames.length 12. windowReference.frames.length 13. links.length 14. selectName.options.length
formName is either the name of a form or an element in the forms array.
frameReference is either the value of the NAME attribute of a frame or an element in the frames array.
radioName is either the value of the NAME attribute of a radio object or an element in the elements array.
selectName is either the value of the NAME attribute of a select object or an element in the elements array.
stringName is any string or a property of an existing object.
windowReference is a valid way of referring to a window, as described in the window object.
The length property is an integer that specifies one of the following:
length is always a read-only property.
For a null string, length is zero. For a select object, the values returned by form 5 and form 14 of the 语法 are the same. For a window containing frames, the values returned by form 7 and form 12 of the 语法 are the same. For a form object, the values returned by form 1 and form 9 of the 语法 are the same. For a frame containing frames, the values returned by form 2 and form 11 of the 语法 are the same.
In the following example, the getChoice() function uses the length property to iterate over every element in the musicType array. musicType is a select element on the musicForm form.
function getChoice() {
for (var i = 0; i < document.musicForm.musicType.length; i++) {
if (document.musicForm.musicType.options[i].selected == true) {
return document.musicForm.musicType.options[i].text
}
}
}
The following example displays 8 in an alert dialog box:
var x="Netscape"
alert("The string length is " + x.length)
Creates an htm hypertext link that jumps to another URL.
linkText.link(hrefAttribute)
linkText is any string or a property of an existing object.
hrefAttribute is any string or a property of an existing object.
Use the link method with the write or writeln methods to programatically create and display a hypertext link in a document. Create the link with the link method, then call write or writeln to display the link in a document.
In the 语法, the linkText string represents the literal text that you want the user to see. The hrefAttribute string represents the HREF attribute of the <A> tag, and it should be a valid URL. Each section of a URL contains different information. See the location object for a 描述 of the URL components.
Links created with the link method become elements in the links array. See the link object for information about the links array.
The following example displays the word "Netscape" as a hypertext link that returns the user to the Netscape home page:
var hotText="Netscape"
var URL="http://www.netscape.com"
document.open()
document.write("Click to return to " + hotText.link(URL))
document.close()
The previous example produces the same output as the following htm:
Click to return to <A HREF="http://www.netscape.com">Netscape</A>
A piece of text or an image identified as a hypertext link. When the user clicks the link text, the link hypertext reference is loaded into its target window.
To define a link, use standard htm 语法 with the addition of the onClick and onMouseOver event handlers:
<A HREF=locationOrURL [NAME="anchorName"] [TARGET="windowName"] [onClick="handlerText"] [onMouseOver="handlerText"]> linkText </A>HREF=locationOrURL identifies a destination anchor or URL. See the location object for a 描述 of the URL components.
You can also define a link using the link method.
To use a link object's properties:
document.links[index].propertyNameindex is an integer representing a link object.
Each link object is a location object and has the same properties as a location object.
If a link object is also an anchor object, the object has entries in both the anchors and links arrays.
When a user clicks a link object and navigates to the destination document (specified by HREF=locationOrURL), the destination document's referrer property contains the URL of the source document. Evaluate the referrer property from the destination document.
You can reference the link objects in your code by using the links array. This array contains an entry for each link object (<A HREF=""> tag) in a document in source order. For example, if a document contains three link objects, these links are reflected as document.links[0], document.links[1], and document.links[2].
To use the links array:
1. document.links[index] 2. document.links.length
index is an integer representing a link in a document.
To obtain the number of links in a document, use the length property: document.links.length.
Elements in the links array are read-only. For example, the statement document.links[0]="link1" has no effect.
The link object has the following properties:
The links array has the following properties:
Example 1. The following example creates a hypertext link to an anchor named javascript_intro.
Example 2. The following example creates a hypertext link to an anchor named numbers in the file DOC3.htm in the window window2. If window2 does not exist, it is created.
Example 3. The following example takes the user back x entries in the history list:
Example 4. The following example creates a hypertext link to a URL. A set of radio buttons lets the user choose between three URLs. The link's onClick event handler sets the URL (the link's href property) based on the selected radio button. The link also has an onMouseOver event handler that changes the window's status property. As the example shows, you must return true to set the window.status property in the onMouseOver event handler.
Example 5: links array. The following example opens the Netscape home page in the newWindow window. The linkGetter() function uses the links array to display the value of each of its links.
A string specifying the color of the document hyperlinks.
document.linkColor
The linkColor property is expressed as a hexadecimal RGB triplet or as one of the string literals listed in Color Values. This property is the JavaScript reflection of the LINK attribute of the <BODY> tag. The default value of this property is set by the user on the Colors tab of the Preferences dialog box, which is displayed by choosing General Preferences from the Options menu. You cannot set this property after the htm source has been through layout.
If you express the color as a hexadecimal RGB triplet, you must use the format rrggbb. For example, the hexadecimal RGB values for salmon are red=FA, green=80, and blue=72, so the RGB triplet for salmon is "FA8072".
The following example sets the color of document links to aqua using a string literal:
document.linkColor="aqua"
The following example sets the color of document links to aqua using a hexadecimal triplet:
document.linkColor="00FFFF"
An array of objects corresponding to link objects in source order. See link object.
The natural logarithm of two, approximately 0.693.
Math.LN2
Because LN2 is a constant, it is a read-only property of Math.
The following example displays the natural log of 2:
document.write("The natural log of 2 is " + Math.LN2)
The natural logarithm of ten, approximately 2.302.
Math.LN10
Because LN10 is a constant, it is a read-only property of Math.
The following example displays the natural log of 10:
document.write("The natural log of 10 is " + Math.LN10)
Contains information on the current URL.
To use a location object:
[windowReference.]location[.propertyName]windowReference is a variable windowVar from a window definition (see window object), or one of the synonyms top or parent.
The location object represents a complete URL. Each property of the location object represents a different portion of the URL.
The following diagram of a URL shows the relationships between the location properties:
protocol//hostname:port pathname search hash
protocol represents the beginning of the URL, up to and including the first colon.
hostname represents the host and domain name, or IP address, of a network host.
port represents the communications port that the server uses for communications.
pathname represents the url-path portion of the URL.
search represents any query information in the URL, beginning with a question mark.
hash represents an anchor name fragment in the URL, beginning with a hash mark (#).
See the properties (listed below) for details about the different parts of the URL, or the href property for 例子.
The location object has two other properties not shown in the diagram above:
href represents a complete URL.
host represents the concatenation hostname:port.
The location object is contained by the window object and is within its scope. If you reference a location object without specifying a window, the location object represents the current location. If you reference a location object and specify a window name, for example, windowReference.location.propertyName, the location object represents the location of the specified window.
Do not confuse the location object with the location property of the document object. You cannot change the value of the location property (document.location), but you can change the value of the location object's properties (window.location.propertyName). document.location is a string-valued property that usually matches what window.location.href is set to when you load the document, but redirection may change it.
When you specify a URL, you can use standard URL formats and JavaScript statements. The following list shows the 语法 for specifying some of the most common types of URLs.
| URL type | Protocol | Example |
|---|---|---|
| JavaScript code | javascript: | javascript:history.go(-1) |
| Navigator info | about: | about:cache |
| World Wide Web | http: | http://www.netscape.com/ |
| File | file: | file:///javascript/methods.htm |
| FTP | ftp: | ftp://ftp.mine.com/home/mine |
| MailTo | mailto: | mailto:info@netscape.com |
| Usenet | news: | news://news.scruznet.com/comp.lang.javascript |
| Gopher | gopher: | gopher.myhost.com |
The javascript: protocol evaluates the expression after the colon (:), if there is one, and loads a page containing the string value of the expression, unless it is undefined. If the expression evaluates to undefined, no new page loads.
The about: protocol provides information on Navigator and has the following 语法:
about:[cache|plugins]about: by itself is the same as choosing About Netscape from the Navigator's Help menu.
Example 1. The following two statements are equivalent and set the URL of the current window to the Netscape home page:
Example 2. The following statement sets the URL of a frame named frame2 to the Sun home page:
相关 the example for the anchor object.
A string specifying the complete URL of the document.
document.location
Do not confuse the location property of the document object with the location object. You cannot change the value of the location property (document.location), but you can change the value of the location object's properties (window.location.propertyName). document.location is a string-valued property that usually matches what window.location.href is set to when you load the document, but redirection may change it.
location is a read-only property of document.
The following example displays the URL of the current document:
document.write("The current URL is " + document.location)
Returns the natural logarithm (base e) of a number.
Math.log(number)number is any positive numeric expression or a property of an existing object.
If the value of number is outside the suggested range, the return value is always -1.797693134862316e+308.
//Displays the value 2.302585092994046
document.write("The natural log of 10 is " + Math.log(10))
//Displays the value 0
document.write("<P>The natural log of 1 is " + Math.log(1))
//Displays the value -1.797693134862316e+308
//because the argument is out of range
document.write("<P>The natural log of 0 is " + Math.log(0))
The base 2 logarithm of e (approximately 1.442).
Math.LOG2E
Because LOG2E is a constant, it is a read-only property of Math.
The following example displays the base 2 logarithm of E:
document.write("The base 2 logarithm of E is " + Math.LOG2E)
The base 10 logarithm of e (approximately 0.434).
Math.LOG10E
Because LOG10E is a constant, it is a read-only property of Math.
The following example displays the base 10 logarithm of E:
document.write("The base 10 logarithm of E is " + Math.LOG10E)