Properties

length

Read/write integer specifying the number of elements in the array, or, when the array does not have contiguous elements, a number one larger than the index of the last element in the array. The length property of a new array is initialized when the array is created with the Array() constructor method. Adding new elements to an array created with the Array() constructor updates the length, if necessary:

a = new Array();    a.length initialized to 0
b = new Array(10);  b.length initialized to 10
c = new Array("one", "two", "three");   c.length initialized to 3
c[3] = "four";  c.length updated to 4
c[10] = "blastoff"; c.length becomes 11

You can also set the value of the length property to change the size of an array (i.e., truncate elements or add "undefined" ones).

Methods

join

Converts each of the elements of an array to a string, and then concatenates those strings, inserting the specified separator string between the elements. Returns the resulting string. You can split a string up into array elements--with the split() method of the String object.

array.join()
array.join(separator)   if no separator, the empty string is used

reverse

Reverse, in place (i.e., without creating a new array), the order of the elements of an array.

sort

With no arguments, sorts alphabetically (by character encoding); elements are first converted to strings, if necessary, so that they can be compared. To sort the array elements in some other order, you must supply a function that compares two values and returns a number indicating their relative order.

array.sort()
array.sort(orderfunc)   orderfunc - optional comparison function

The comparison function should take two arguments, a and b, and should:

• Return a value less than zero if, according to your sort criteria, a is less than b, and should appear before b in the sorted array.

• Return zero if a and b are equivalent for the purposes of this sort.

• Return a value greater than zero if a is greater than b for the purposes of the sort.

Methods

toString()

Returns true or false, depending on the boolean value represented by the Boolean object.

valueOf()

Returns the boolean value represented by the Boolean object.

Properties

form

Read-only reference to the Form object that contains the specified button object.

name

Set by the name attribute of the HTML <input> tag that creates the button, this read-only string property provides the name of the button.

form.button_name
form.elements['button_name']

type

See the type property of the Element object (Element.type).

value

Set by the value attribute of the HTML <input> tag that creates the button, this read-only string property provides text displayed in the Button object.

Event Handlers

onClick()

Invoked when the button is clicked; defined by the onClick attribute of the HTML <input> tag. Value may be any number of JavaScript statements, separated by semicolons, that are executed when the user clicks the button.

<INPUT TYPE="button" a definition of the handler
       value="button-text"
       onClick="handler-statements">
button.onclick    a reference to the handler
button.onclick()  an explicit invocation of the handler

HTML syntax

A Button object is created with a standard HTML <input> tag, with the addition of the onClick attribute:

<form>
    ...
  <input
    type="button"   specifies that this is a button
    value="label" the text that is to appear within the button;
        specifies the value property
    [ name="name" ]   a name that can later be used to refer to the button;
    specifies the name property
    [ onClick="handler" ] JavaScript statements to be executed
    when the button is clicked
  >
    ...
</form>

Properties

checked

Read/write Boolean property that specifies whether the Checkbox is checked (true) or not (false). Setting the checked property changes the appearance of the Checkbox but does not cause the onclick() event handler to be invoked.

defaultChecked

Read-only Boolean property that represents the Checkbox's initial state. May be specified using the checked attribute in the HTML <input> tag. Can be used to reset a Checkbox to its default state.

form

Read-only reference to the Form object that contains the Checkbox.

name

Read-only string, set by the HTML name attribute, that specifies the name of the Checkbox object (or array of Checkbox objects).

type

See the type property of the Element object (Element.type).

value

Read/write string that specifies the text that is passed to the Web server if the Checkbox is checked when the form is submitted. The initial value of value is specified by the HTML value attribute. If no value attribute is specified, then the default value string is "on."

Event handlers

onclick()

Invoked when the user clicks on a Checkbox; it is defined by the HTML onClick attribute. The value of this attribute may be any number of JavaScript statements, separated by semicolons, which are executed when the user clicks on the Checkbox.

<INPUT type="checkbox"   a definition of the handler
       onClick="handler-statements">
checkbox.onclick  a reference to the handler
checkbox.onclick();   an explicit invocation of the handler

HTML syntax

A Checkbox object is created with a standard HTML <input> tag, with the addition of the new onClick attribute. Multiple Checkbox objects are often created in groups by specifying multiple <input> tags which have the same name attribute.

<form>
    ...
  <input
    type="checkbox" specifies that this is a checkbox
    [ name="name" ]   a name that can later be used to refer to this checkbox
    or to the group of checkboxes with this name;
    specifies the name property
    [ value="value" ] the value returned when this checkbox is selected;
    specifies the value property
    [ checked ] specifies that the checkbox is initially checked
    Specifies the defaultChecked property
    [ onClick="handler" ] JavaScript statements to be executed when the
    Checkbox is clicked
  >
label the HTML text that should appear next to the Checkbox
    ...
</form>

Methods

getDate()

Returns the day of the month of a Date object. Return values are between 1 and 31.

getDay()

Returns the day of the week of a Date object. Return values are between 0 (Sunday) and 6 (Saturday).

getHours()

Returns the hours field of a Date object. Return values are between 0 (midnight) and 23 (11 PM).

getMinutes()

Returns the minutes field of a Date object. Return values are between 0 and 59.

getMonth()

Returns the month field of a Date object. Return values are between 0 (January) and 11 (December).

getSeconds()

Returns the seconds field of a Date object. Return values are between 0 and 59.

getTime()

Returns the internal, millisecond representation of a Date object (i.e., the number of milliseconds between midnight GMT on 1/1/1970 and the specified date).

getTimezoneOffset()

Returns the difference in minutes between this date (in the local time zone) and GMT. Tells you what time zone the JavaScript code is running in. Since getTimezoneOffset is invoked through a Date object, but doesn't reference the Date object, it should actually be its own function.

getYear()

Returns the year field of a Date object. Return value is the year minus 1900 (e.g., 96 for 1996).

parse()

Parses a string representation of a date and returns it in millisecond format.

setDate()

Sets the day of the month field of a Date object.

date.setDate(day_of_month) // day_of_month is 1-31

setHours()

Sets the hour field of a Date object.

date.setHours(hours) //hours is integer betw 0
(midnight) and 23 (11pm)

setMinutes()

Sets the minutes field of a Date object.

date.setMinutes(minutes) //minutes is integer betw 0 and 59

setMonth()

Sets the month field of a Date object.

date.setMonth(month) //month is integer betw 0 (Jan) and 11 (Dec)

setSeconds()

Sets the seconds field of a Date object.

date.setSeconds(seconds) //seconds is integer betw 0 and 59

setTime()

Sets a Date object in the milliseconds between the desired date/time and midnight GMT on January 1, 1970. Representing a date in this millisecond format makes it independent of time zone.

date.setTime(milliseconds)

setYear()

Sets the year field of a Date object.

date.setYear(year)  // year is year minus 1900; e.g. 96 for 1996

toGMTString()

Converts a Date to a string, using the GMT time zone; format of string varies slightly according to platform.

toLocaleString()

Converts a Date to a string, using the local time zone; uses local conventions for data and time formatting.

UTC()

Converts a numeric date and time specification to millisecond format.

Properties

Note that for all attributes to set a color, the value can be one of the standard color names recognized by JavaScript, or an RGB value in six hexadecimal digits (RRGGBB).

alinkColor

String that specifies the color of activated links (i.e., links being selected by user). Can be set directly in the document <head>, or inherited from the alink attribute in the <body>.

anchors[]

An array of Anchor objects, one for each anchor (i.e., hypertext target) in the document.

anchors.length

Read-only integer specifying the number of elements in the anchors[] array.

applets[]

An array of Java objects, one for each <applet> that appears in the document.

applets.length

A read-only integer specifying the number of elements in the applets[] array.

bgColor

String that specifies the background color of the document. Can be set directly at any point in document, or inherited from the bgcolor attribute in the <body>. Buggy in Netscape 2.0.

cookie

A string that is the value of a cookie associated with this document. String property that allows you to read, create, modify, and delete the cookie(s) that apply to the current document. A "cookie" is a small amount of named data stored by the Web browser so that it can use data input on one page in another page, or recall user preferences across Web-browsing sessions.

document.cookie

The read and write values of the cookie property generally differ. In a JavaScript expression, the cookie property returns a string containing all the cookies from the current document, in name=value pairs (separated by semicolons). Use String.indexOf() and String.substring() to determine the value of a particular cookie. Since cookies cannot contain any semicolons, commas, or whitespace, they are commonly encoded using escape() before storing and decoded using unescape() after retrieving.

To associate a cookie value with the current document for the current Web browsing session, set document.cookie to a string of the form name=value. To create a cookie that can last across browser sessions, include an expiration date by setting document.cookie to a string of the form:

name=value; expires=date

date should be a date specification in the format written by Date.toGMTString().

domain

String that specifies the Internet domain which the document is from; used for security purposes.

embeds[]

An array of Java objects, one for each <embed> tag that appears in the document.

embeds.length

Read-only integer that specifies the number of elements in the embeds[] array.

fgColor

String that specifies the default color of document text. Can be set directly in the document <head>, or inherited from the text attribute in the <body>.

forms[]

An array of Form objects, one for each <form> that appears in the document.

forms.length

Read-only integer specifying the number of elements in the forms[] array.

images[]

An array of Image objects, one for each image embedded in the document with the <img> tag.

images.length

The number of elements in the images[] array.

lastModified

Read-only string that contains the (local) date and time at which document was most recently modified (derived from the HTTP header).

linkColor

String that specifies the color of unvisited links. Can be set directly in the document <head>, or inherited from the link attribute in the <body>.

links[]

An array of Link objects, one for each hypertext link in the document.

links.length

Read-only integer specifying the number of elements in the links[] array.

location

Synonym for the URL property. Use URL instead because it is less likely to be confused with the Window.location property.

plugins[]

Synonym for the embeds[] array.

plugins.length

The number of elements in the plugins[] or embeds[] array.

referrer

Read-only string that contains the URL of the document from which the current document was reached.

title

Read-only string that specifies the <title> of the document.

URL

Read-only string that specifies the URL of the document that contained the link that referred to the current document.

vlinkColor

String that specifies the color of visited links. Can be set directly in the document <head>, or inherited from the vlink attribute in the <body>.

Methods

clear()

Clears the window or frame that contains document.

close()

Displays any output to document that has been written but not yet displayed, and closes the output stream.

open()

Opens a stream to document, so that subsequent document.write() calls can append data to the document.

write()