Returns the tangent of a number.
Math.tan(number)
number is a numeric expression representing the size of an angle in radians, or a property of an existing object.
The tan method returns a numeric value which represents the tangent of the angle.
//Displays the value 0.9999999999999999
document.write("The tangent of pi/4 radians is " +
Math.tan(Math.PI/4))
//Displays the value 0
document.write("<P>The tangent of 0 radians is " +
Math.tan(0))
For form, a string specifying the name of the window that responses go to after a form has been submitted. For link, a string specifying the name of the window that displays the content of a clicked hypertext link.
1. formName.target 2. links[index].target
formName is either the name of a form or an element in the forms array.
index is an integer representing a link object.
The target property initially reflects the TARGET attribute of the <FORM> and <A> tags; however, setting target overrides these attributes.
The target property cannot be assigned the value of a JavaScript expression or variable.
You can set the target property at any time.
Certain values of the target property may require specific values for other form properties. See RFC 1867 for more information.
The following example specifies that responses to the musicInfo form are displayed in the "msgWindow" window:
document.musicInfo.target="msgWindow"
For form:
A text input field on an htm form. A text field lets the user enter a word, phrase, or series of numbers.
To define a text object, use standard htm 语法 with the addition of the onBlur, on Change, onFocus, and onSelect event handlers:
<INPUT TYPE="text" NAME="textName" VALUE="textValue" SIZE=integer [onBlur="handlerText"] [onChange="handlerText"] [onFocus="handlerText"] [onSelect="handlerText"]>NAME="textName" specifies the name of the text object. You can access this value using the name property.
To use a text object's properties and methods:
1. textName.propertyName 2. textName.methodName(parameters) 3. formName.elements[index].propertyName 4. formName.elements[index].methodName(parameters)textName is the value of the NAME attribute of a text object.
A text object on a form looks as follows:
A text object is a form element and must be defined within a <FORM> tag.
text objects can be updated (redrawn) dynamically by setting the value property (this.value).
Example 1. The following example creates a text object that is 25 characters long. The text field appears immediately to the right of the words "Last name:". The text field is blank when the form loads.
Example 2. The following example creates two text objects on a form. Each object has a default value. The city object has an onFocus event handler that selects all the text in the field when the user tabs to that field. The state object has an onChange event handler that forces the value to upper case.
相关 the 例子 for the onBlur, onChange, onFocus, and onSelect event handlers.
A string specifying the text that follows an <OPTION> tag in a select object.
selectName.options[index].text
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.
options array
The text property initially reflects the text that follows an <OPTION> tag in a select object.
You can set the text property at any time; however, the following effects result:
Be careful if you change the text property. If you evaluate the property after you change it, the property contains the new value, not the value that is displayed onscreen.
In the following example, the getChoice() function returns the value of the text property for the selected option. The for loop evaluates every option in the musicType select object. The if statement finds the option that is selected.
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
}
}
return null
}
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>
A multiline input field on an htm form. A textarea field lets the user enter words, phrases, or numbers.
To define a text area, use standard htm 语法 with the addition of the onBlur, onChange, onFocus, and onSelect event handlers:
<TEXTAREA NAME="textareaName" ROWS="integer" COLS="integer" WRAP="off|virtual|physical" [onBlur="handlerText"] [onChange="handlerText"] [onFocus="handlerText"] [onSelect="handlerText"]> textToDisplay </TEXTAREA>NAME="textareaName" specifies the name of the textarea object. You can access this value using the name property.
The WRAP attribute controls word wrapping inside the TEXTAREA. The value "off" is default and lines are sent exactly as typed. The value "virtual" wraps in the display but are sent exactly as typed. The value "physical" wraps in the display and sends new-lines at the wrap points as if new-lines had been entered.
To use a textarea object's properties and methods:
1. textareaName.propertyName 2. textareaName.methodName(parameters) 3. formName.elements[index].propertyName 4. formName.elements[index].methodName(parameters)textareaName is the value of the NAME attribute of a textarea object.
A textarea object on a form looks as follows:
A textarea object is a form element and must be defined within a <FORM> tag.
textarea objects can be updated (redrawn) dynamically by setting the value property (this.value).
To begin a new line in a textarea object, you can use a newline character. This character varies from platform to platform: Unix is \n, Windows is \r\n, and Macintosh is \n. One way to enter a newline character programatically is to test the appVersion property to determine the current platform and set the newline character accordingly. See the appVersion property for an example.
The following example creates a textarea object that is 6 rows long and 55 columns wide. The textarea field appears immediately below the word "描述:". When the form loads, the textarea object contains several lines of data, including one blank line.
相关 the 例子 for the onBlur, onChange, onFocus, and onSelect event handlers.
A string representing the title of a document.
document.title
The title property is a reflection of the value specified within the <TITLE> and </TITLE> tags. If a document does not have a title, the title property is null.
title is a read-only property.
In the following example, the value of the title property is assigned to a variable called docTitle:
var newWindow = window.open("http://www.netscape.com")
var docTitle = newWindow.document.title
Converts a date to a string, using the Internet GMT conventions.
dateObjectName.toGMTString()
dateObjectName is either the name of a date object or a property of an existing object.
The exact format of the value returned by toGMTString varies according to the platform.
today.toGMTString()
In this example, the toGMTString method converts the date to GMT (UTC) using the operating system's time zone offset and returns a string value that is similar to the following form. The exact format depends on the platform.
Mon, 18 Dec 1995 17:28:35 GMT
Converts a date to a string, using the current locale's conventions.
dateObjectName.toLocaleString()
dateObjectName is either the name of a date object or a property of an existing object.
today.toLocaleString()
In this example, toLocaleString returns a string value that is similar to the following form. The exact format depends on the platform.
12/18/95 17:28:35
Returns the calling string value converted to lower case.
stringName.toLowerCase()
stringName is any string or a property of an existing object.
The toLowerCase method returns the value of stringName converted to lower case. toLowerCase does not affect the value of stringName itself.
The following 例子 both yield "alphabet".
var upperText="ALPHABET" document.write(upperText.toLowerCase()) "ALPHABET".toLowerCase()
The top property is a synonym for the top-most Navigator window, which is a "document window" or "Web Browser window."
1. top.propertyName 2. top.methodName 3. top.frameName 4. top.frames[index]
propertyName is defaultStatus, status, or length.
methodName is any method associated with the window object.
frameName and frames[index] are ways to refer to frames.
The top property refers to the top-most window that contains frames or nested framesets. Use the top property to refer to this ancestor window.
The top property is read-only. The value of the top property is
<object objectReference>where objectReference is an internal reference.
The statement top.close() closes the top-most ancestor window.
The statement top.length specifies the number of frames contained within the top-most ancestor window. When the top-most ancestor is defined as follows, top.length returns 3:
<FRAMESET COLS="30%,40%,30%"> <FRAME SRC=child1.htm NAME="childFrame1"> <FRAME SRC=child2.htm NAME="childFrame2"> <FRAME SRC=child3.htm NAME="childFrame3"> </FRAMESET>
The following example sets the background color of a frame called myFrame to red. myFrame is a child of the top-most ancestor window.
top.myFrame.document.bgColor="red"
Returns the calling string value converted to upper case.
stringName.toUpperCase()
stringName is any string or a property of an existing object.
The toUpperCase method returns the value of stringName converted to upper case. toUpperCase does not affect the value of stringName itself.
The following 例子 both yield "ALPHABET".
var lowerText="alphabet" document.write(lowerText.toUpperCase()) "alphabet".toUpperCase()
Returns the ASCII string for the specified value.
unescape("string")
string is a string or a property of an existing object, containing characters in either of the following forms:
The unescape function is not a method associated with any object, but is part of the language itself.
The string returned by the unescape function is a series of characters in the ISO Latin-1 character set.
The following example returns "&"
unescape("%26")
The following example returns "!#"
unescape("%21%23")
A string representing the value of the user-agent header sent in the HTTP protocol from client to server.
navigator.userAgent
Servers use the value sent in the user-agent header to identify the client.
userAgent is a read-only property.
The following example displays userAgent information for the Navigator:
document.write("The value of navigator.userAgent is " +
navigator.userAgent)
For Navigator 2.0, this displays the following:
The value of navigator.userAgent is Mozilla/2.0 (Win16; I)
Returns the number of milliseconds in a date object since January 1, 1970 00:00:00, Universal Coordinated Time (GMT).
Date.UTC(year, month, day [, hrs] [, min] [, sec])
year is a year after 1900.
month is a month between 0-11.
date is a day of the month between 1-31.
hrs is hours between 0-23.
min is minutes between 0-59.
sec is seconds between 0-59.
UTC takes comma-delimited date parameters and returns the number of milliseconds since January 1, 1970 00:00:00, Universal Coordinated Time (GMT).
Because UTC is a static 用法 Date, you always use it as Date.UTC(), rather than as a 用法 a date object you created.
The following statement creates a date object using GMT instead of local time:
gmtDate = new Date(Date.UTC(96, 11, 1, 0, 0, 0))
A string that is related to the VALUE attribute of its object.
1. objectName.value 2. radioName[index].value 3. selectName.options.[index].value
objectName is either the value of the NAME attribute of a hidden, password, text, textarea, button, reset, submit or checkbox object or an element in the elements array.
radioName is the value of the NAME attribute of a radio object.
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 a radio button in a radio object or an option in a select object.
The value property differs for every object.
You can set the value property at any time. The display of the text and textarea objects updates immediately when you set the value property.
The value property is a string that initially reflects the VALUE attribute. This string is represented by asterisks in the password object field. The value of this property changes when a user or a program modifies the field, but the value is always displayed as asterisks.
If you programatically set the value property and then evaluate it, JavaScript returns the current value. If a user interactively modifies the value in the password field, you cannot evaluate it accurately for security reasons.
When a VALUE attribute is specified in htm, the value property is a string that reflects it. This string is displayed on the face of the button.
When a VALUE attribute is not specified in htm, the value property differs for each object:
These strings are displayed on the faces of the buttons.
value is a read-only property.
Do not confuse the value property with the name property. The name property is not displayed onscreen; it is used to reference the objects programatically.
The value property is a string that initially reflects the VALUE attribute. The value of this property can change when a program modifies it. The value property is not displayed onscreen, but is returned to the server if the option is selected.
You can set the value property at any time.
Do not confuse the value property with the selection state of the select object or the text that is displayed as an option. The selected and selectedIndex properties determine which options are selected, and the defaultSelected property determines the default selection state. The text that is displayed in each option is specified by its text property.
When a VALUE attribute is specified in htm, the value property is a string that reflects it. When a VALUE attribute is not specified in htm, the value property is a string that evaluates to "on". The value property is not displayed onscreen, but is returned to the server if the radio button or checkbox is selected.
You can set the value property at any time.
Do not confuse the value property with the selection state of the object or the text that is displayed next to each checkbox and radio button. The checked property determines the selection state of the object, and the defaultChecked property determines the default selection state. The text that is displayed is specified following the <INPUT TYPE="checkbox"> or the <INPUT TYPE="radio"> tag.
The following function evaluates the value property of a group of buttons and displays it in the msgWindow window:
function valueGetter() {
var msgWindow=window.open("")
msgWindow.document.write("submitButton.value is " +
document.valueTest.submitButton.value + "<BR>")
msgWindow.document.write("resetButton.value is " +
document.valueTest.resetButton.value + "<BR>")
msgWindow.document.write("helpButton.value is " +
document.valueTest.helpButton.value + "<BR>")
msgWindow.document.close()
}
This example displays the following values:
Query Submit Reset Help
The previous example assumes the buttons have been defined as follows
<INPUT TYPE="submit" NAME="submitButton"> <INPUT TYPE="reset" NAME="resetButton"> <INPUT TYPE="button" NAME="helpButton" VALUE="Help">
The following function evaluates the value property of a group of radio buttons and displays it in the msgWindow window:
function valueGetter() {
var msgWindow=window.open("")
for (var i = 0; i < document.valueTest.radioObj.length; i++) {
msgWindow.document.write
("The value of radioObj[" + i + "] is " +
document.valueTest.radioObj[i].value +"<BR>")
}
msgWindow.document.close()
}
This example displays the following values:
on on on on
The previous example assumes the buttons have been defined as follows
<BR><INPUT TYPE="radio" NAME="radioObj">R&B <BR><INPUT TYPE="radio" NAME="radioObj" CHECKED>Soul <BR><INPUT TYPE="radio" NAME="radioObj">Rock and Roll <BR><INPUT TYPE="radio" NAME="radioObj">Blues
For hidden, password, text, and textarea:
For button, reset, and submit:
For options array:
For checkbox and radio:
A string specifying the color of visited links.
document.vlinkColor
The vlinkColor 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 VLINK 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 visited links to aqua using a string literal:
document.vlinkColor="aqua"
The following example sets the color of active links to aqua using a hexadecimal triplet:
document.vlinkColor="00FFFF"
The top-level object for each document, location, and history object group.
To define a window, use the open method:
windowVar = window.open("URL", "windowName" [,"windowFeatures"])
windowVar is the name of a new window. Use this variable when referring to a window's properties, methods, and containership.
For details on defining a window, see the open method.
To use a window object's properties and methods:
1. window.propertyName 2. window.methodName(parameters) 3. self.propertyName 4. self.methodName(parameters) 5. top.propertyName 6. top.methodName(parameters) 7. parent.propertyName 8. parent.methodName(parameters) 9. windowVar.propertyName 10. windowVar.methodName(parameters) 11. propertyName 12. methodName(parameters)windowVar is a variable referring to a window object. See the preceding 语法 for defining a window.
To define an onLoad or onUnload event handler for a window object, use the <BODY> or <FRAMESET> tags:
<BODY ... [onLoad="handlerText"] [onUnload="handlerText"]> </BODY> <FRAMESET ROWS="rowHeightList" COLS="columnWidthList" [onLoad="handlerText"] [onUnload="handlerText"]> [<FRAME SRC="locationOrURL" NAME="frameName">] </FRAMESET>
For information on the <BODY> and <FRAMESET> tags, see the document and frame objects.
The window object is the top-level object in the JavaScript client hierarchy. Frame objects are also windows.
The self and window properties are synonyms for the current window, and you can optionally use them to refer to the current window. For example, you can close the current window by calling either window.close() or self.close(). You can use these properties to make your code more readable, or to disambiguate the property reference self.status from a form called status. See the properties and methods listed below for more 例子.
The top and parent properties are also synonyms that can be used in place of the window name. top refers to the top-most Navigator window, and parent refers to a window containing a frameset. See the top and parent properties.
Because the existence of the current window is assumed, you do not have to reference the name of the window when you call its methods and assign its properties. For example, status="Jump to a new location" is a valid property assignment, and close() is a valid method call. However, when you open or close a window within an event handler, you must specify window.open() or window.close() instead of simply using open() or close(). Due to the scoping of static objects in JavaScript, a call to close() without specifying an object name is equivalent to document.close().
You can reference a window's frame objects in your code by using the frames array. The frames array contains an entry for each frame in a window with a <FRAMESET> tag.
Windows lack event handlers until some htm is loaded into them containing a <BODY> or <FRAMESET> tag.
The following objects are also properties of the window object:
In the following example, the document in the top window opens a second window, window2, and defines pushbuttons that open a message window, write to the message window, close the message window, and close window2. The onLoad and onUnload event handlers of the document loaded into window2 display alerts when the window opens and closes.
WIN1.htm, which defines the frames for the first window, contains the following code:
WIN2.htm, which defines the content for window2, contains the following code:
相关 the example for the frame object.
The window property is a synonym for the current window or frame.
1. window.propertyName 2. window.methodName
propertyName is the defaultStatus, status, length, or name property when the calling window refers to a window object.
propertyName is the length or name property when the calling window refers to a frame object.
methodName is any method associated with the window object.
The window property refers to the current window or frame.
Although you can use the window property as a synonym for the current frame, your code is more readable if you use the self property. For example, window.name and self.name both specify the name of the current frame, but self.name is easier to understand.
Use the window property to disambiguate a property of the window object from a form or form element of the same name. You can also use the window property to make your code more readable.
The window property is read-only. The value of the window property is
<object nameAttribute>where nameAttribute is the NAME attribute if window refers to a frame, or an internal reference if window refers to a window.
In the following example, window.status is used to set the status property of the current window. This usage disambiguates the status property of the current window from a form called "status" within the current window.
Writes one or more htm expressions to a document in the specified window.
document.write(expression1 [,expression2], ...[,expressionN])expression1 through expressionN are any JavaScript expressions or the properties of existing objects.
The write method displays any number of expressions in a document window. You can specify any JavaScript expression with the write method, including numerics, strings, or logicals.
The write method is the same as the writeln method, except the write method does not append a newline character to the end of the output.
Use the write method within any <SCRIPT> tag or within an event handler. Event handlers execute after the original document closes, so the write method will implicitly open a new document of mimeType text/htm if you do not explicitly issue a document.open() method in the event handler.
var mystery = "world"
// Displays Hello world testing 123
msgWindow.document.write("Hello ", mystery, " testing ", 123)
In the following example, the write method takes two arguments. The first argument is an assignment expression, and the second argument is a string literal.
//Displays Hello world... msgWindow.document.write(mystr = "Hello "+ "world...")In the following example, the write method takes a single argument that is a conditional expression. If the value of the variable age is less than 18, the method displays "Minor". If the value of age is greater than or equal to 18, the method displays "Adult".
msgWindow.document.write(status = (age >= 18) ? "Adult" : "Minor")
Writes one or more htm expressions to a document in the specified window and follows them with a newline character.
document.writeln(expression1 [,expression2], ...[,expressionN])expression1 through expressionN are any JavaScript expressions or the properties of existing objects.
The writeln method displays any number of expressions in a document window. You can specify any JavaScript expression, including numerics, strings, or logicals.
The writeln method is the same as the write method, except the writeln method appends a newline character to the end of the output. htm ignores the newline character, except within certain tags such as <PRE>.
Use the writeln method within any <SCRIPT> tag or within an event handler. Event handlers execute after the original document closes, so the writeln method will implicitly open a new document of mimeType text/htm if you do not explicitly issue a document.open() method in the event handler.
All the 例子 used for the write method are also valid with the writeln method.