JavaScript Language Reference
JavaScript Language Reference
The first part of this reference is organized by object with properties
and methods listed by the object they apply to. The second part covers
independent functions in JavaScript not connected with a particular object,
as well as operators in JavaScript.
The anchor
Object
See the anchors property of the document object.
The button Object
The button object reflects a push button from an HTML form in JavaScript.
Properties
-
name A string value containing the name of the button element.
-
value A string value containing
the value of the button element.
Methods
-
click() Emulates the action of
clicking on the button.
Event Handlers
-
onClick Specifies JavaScript code
to execute when the button is clicked.
The checkbox
Object
The checkbox object makes a checkbox from an HTML form available
in JavaScript.
Properties
-
checked A boolean value indicating
if the checkbox element is checked.
-
defaultChecked A boolean value
indicating if the checkbox element was checked by default (i.e. reflects
the CHECKED attribute).
-
name A string value containing
the name of the checkbox element.
-
value A string value containing
the value of the checkbox element.
Methods
-
click() Emulates the action of
clicking on the checkbox.
Event Handlers
-
onClick Specifies JavaScript code
to execute when the checkbox is clicked.
The Date
Object
The Date object provides mechanisms for working with dates and times
in JavaScript. Instances of the object can be created with the syntax
newObjectName = new Date(dateInfo)
Where dateInfo is an optional specification of a particular
date and can be one of the following:
"month day, year hours:minutes:seconds"
year, month, day
year, month, day, hours, minutes, seconds
where the later two options represent integer values.
If no dateInfo is specified, the new object will represent
the current date and time.
Methods
-
getDate() Returns the day of the
month for the current Date object as an integer from 1 to 31.
-
getDay() Returns the day of the
week for the current Date object as an integer from 0 to 6 (where
0 is Sunday, 1 is Monday, etc.).
-
getHours() Returns the hour from
the time in the current Date object as an integer from 0 to 23.
-
getMinutes() Returns the minutes
from the time in the current Date object as an integer from 0 to
59.
-
getMonth() Returns the month for
the current Date object as an integer from 0 to 11 (where 0 is January,
1 is February, etc.).
-
getSeconds() Returns the seconds
from the time in the current Date object as an integer from 0 to
59.
-
getTime() Returns the time of
the current Date object as an integer representing the number of
milliseconds since 1 January 1970 at 00:00:00.
-
getTimezoneOffset() Returns the
difference between the local time and GMT as an integer representing the
number of minutes.
-
getYear() Returns the year of
the week for the current Date object as a two-digit integer representing
the year less 1900.
-
parse(dateString) Returns the
number of milliseconds between January 1, 1970 at 00:00:00 and the date
specified in dateString. dateString should
take the format
Day, DD Mon YYYY HH:MM:SS TZN
Mon DD, YYYY
-
setDate(dateValue) Sets
the day of the month for the current Date object. dateValue
is an integer from 1 to 31.
-
setHours(hoursValue) Sets
the hours for the time for the current Date object. hoursValue
is an integer from 0 to 23.
-
setMinutes(minutesValue)
Sets the minutes for the time for the current Date object. minutesValue
is an integer from 0 to 59.
-
setMonth(monthValue) Sets
the month for the current Date object. monthValue
is an integer from 0 to 11 (where 0 is January, 1 is February, etc.).
-
setSeconds(secondsValue)
Sets the seconds for the time for the current Date object. secondsValue
is an integer from 0 to 59.
-
setTime(timeValue) Sets
the value for the current Date object. timeValue is
an integer representing the number of milliseconds since January 1, 1970
at 00:00:00.
-
setYear(yearValue) Sets
the year for the current Date object. yearValue is
an integer greater than 1900.
-
toGMTString() Returns the value
of the current Date object in GMT as a string using Internet conventions
in the form
Day, DD Mon YYYY HH:MM:SS GMT
-
toLocaleString() Returns the value
of the current Date object in the local time using local conventions.
-
UTC(yearValue, monthValue, dateValue,
hoursValue, minutesValue, secondsValue) Returns the number of milliseconds
since January 1, 1970 at 00:00:00 GMT. yearValue is an integer greater
than 1900. monthValue is an integer from 0 to 11. dateValue
is an integer from 1 to 31. hoursValue is an integer from 0 to 23.
minutesValue and secondsValue are integers from 0 to 59.
hoursValue, minutesValue and secondsValue are optional.
The document
Object
The document object reflects attributes of an HTML document in JavaScript.
Properties
-
alinkColor The color of active
links as a string or a hexadecimal triplet.
-
anchors Array of anchor objects
in the order they appear in the HTML document. Use anchors.length
to get the number of anchors in a document.
-
bgColor The color of the document's
background.
-
cookie A string value containing
cookie values for the current document.
-
fgColor The color of the document's
foreground.
-
forms Array of form objects in
the order the forms appear in the HTML file. Use forms.length to
get the number of forms in a document.
-
lastModified String value containing
the last date of modification of the document.
-
linkColor The color of links as
a string or a hexadecimal triplet.
-
links Array of link objects in
the order the hypertext links appear in the HTML document. Use links.length
to get the number of links in a document.
-
location A string containing the
URL of the current document.
-
referrer A string value containing
the URL of the calling document when the user follows a link.
-
title A string containing the
title of the current document.
-
vlinkColor The color of followed
links as a string or a hexadecimal triplet.
Methods
-
clear() Clears the document window.
-
close() Closes the current output
stream.
-
open(mimeType) Opens a stream
which allows write() and writeln() methods to write to the
document window. mimeType is an optional string which specifies
a document type supported by Navigator or a plug-in (i.e. text/html,
image/gif, etc.).
-
write() Writes text and HTML to
the specified document.
-
writeln() Writes text and HTML
to the specified document followed by a newline character.
The form
Object
The form object reflects an HTML form in JavaScript. Each HTML form
in a document is reflected by a distinct instance of the form object.
Properties
-
action A string value specifying
the URL which the form data is submitted to.
-
elements Array of objects for
each form element in the order in which they appear in the form.
-
encoding String containing the MIME encoding of the form
as specified in the ENCTYPE attribute.
-
method A string value containing
the method of submission of form data to the server.
-
target A string value containing
the name of the window that responses to form submissions are directed
to.
Methods
-
submit() Submits the form.
Event Handlers
-
onSubmit Specifies JavaScript
code to execute when the form is submitted. The code should return a true
value to allow the form to be submitted. A false value prevents the form
from being submitted.
The frame
Object
The frame object reflects a frame window in JavaScript.
Properties
-
frames An array of objects for
each frame in a window. Frames appear in the array in the order in which
they appear in the HTML source code.
-
parent A string indicating the
name of window containing the frameset.
-
self A alternative for the name
of the current window.
-
top An alternative for the name
of the top-most window.
-
window An alternative for the
name of the current window.
Methods
-
alert(message) Displays
message in a dialog box.
-
close() Closes the window.
-
confirm(message) Displays
message in a dialog box with OK and CANCEL buttons. Returns
true or false based on the button clicked by the user.
-
open(url,name,features) Opens
url in a window named name. If name
doesn't exist, a new window is created with that name. features
is an optional string argument containing a list of features for the new
window. The feature list contains any of the following name-value pairs
separated by commas and without additional spaces:
toolbar=[yes,no,1,0]
|
Indicates if the window should have a toolbar
|
location=[yes,no,1,0]
|
Indicates if the window should have a location field
|
directories=[yes,no,1,0]
|
Indicates is the window should have directory buttons
|
status=[yes,no,1,0]
|
Indicates if the window should have a status bar
|
menubar=[yes,no,1,0]
|
Indicates if the window should have menus
|
scrollbars=[yes,no,1,0]
|
Indicates if the window should have scroll bars
|
resizable=[yes,no,1,0]
|
Indicates if the window should be resizable
|
width=pixels
|
Indicates the width of the window in pixels
|
height=pixels
|
Indicates the height of the window in pixels
|
-
prompt(message,response) Displays
message in a dialog box with a text entry field with the
default value of response. The user's response in the text entry
field is returned as a string.
-
setTimeout(expression,time)
Evaluates expression after time where time
is a value in milliseconds. The time out can be named with the structure:
name = setTimeOut(expression,time)
-
clearTimeout(name) Cancels
the time out with the name name.
The hidden
Object
The hidden object reflects a hidden field from an HTML form in JavaScript.
Properties
-
name A string value containing the name of the hidden element.
-
value A string value containing the value of hidden text
element.
The history Object
The history object allows a script to work with the Navigator browser's
history list in JavaScript. For security and privacy reasons, the actual
content of the list is not reflected into JavaScript.
Properties
-
length An integer representing
the number of items on the history list.
Methods
-
back() Goes back to the previous
document in the history list.
-
forward() Goes forward to the
next document in the history list.
-
go(location) Goes to the document
in the history list specified by location. location
can be a string or integer value. If it is a string it represents all or
part of a URL in the history list. If it is an integer, location
represents the relative position of the document on the history list. As
an integer, location can be positive or negative.
The link
object
The link object reflects a hypertext link in the body of a document.
Properties
-
target A string value containing
the name of the window or frame specified in the TARGET attribute.
Event Handlers
-
onClick Specifies JavaScript
code to execute when the link is clicked.
-
onMouseOver Specifies JavaScript
code to execute when the mouse is over the hypertext link
The location
Object
The location object reflects information about the current URL.
Properties
-
hash A string value containing
the anchor name in the URL.
-
host A string value containing
the hostname and port number from the URL.
-
hostname A string value containing
the domain name (or numerical IP address) from the URL.
-
href A string value containing
the entire URL.
-
pathname A string value specifying
the path portion of the URL.
-
port A string value containing
the port number from the URL.
-
protocol A string value containing
the protocol from the URL (including the colon, but not the slashes).
-
search A string value containing
any information passed to a GET CGI-BIN call (i.e. an information
after the question mark).
The Math
Object
The Math object provides properties and methods for advanced mathematical
calculations.
Properties
-
E The value of Euler's constant
(roughly 2.718) used as the base for natural logarithms.
-
LN10 The value of the natural
logarithm of 10 (roughly 2.302).
-
LN2 The value of the natural
logarithm of 2 (roughly 0.693).
-
PI The value of PI[md]used in
calculating the circumference and area of circles (roughly 3.1415).
-
SQRT1_2 The value of the square
root of one-half (roughly 0.707).
-
SQRT2 The value of the square
root of two (roughly 1.414).
Methods
-
abs(number) Returns the absolute
value of number. The absolute value is the value of a number
with it's sign ignored so abs(4) and abs(-4) both return
4
-
acos(number) Returns
the arc cosine of number in radians.
-
asin(number) Returns
the arc sine of number in radians.
-
atan(number) Returns
the arc tangent of number in radians.
-
ceil(number) Returns
the next integer greater than number[md]in other words, rounds
up to the next integer.
-
cos(number) Returns the cosine
of number where number represents an angle
in radians.
-
exp(number) Returns the value
of E to the power of number.
-
floor(number) Returns
the next integer less than number[md]in other words, rounds
down to the nearest integer.
-
log(number) Returns the natural
logarithm of number.
-
max(number1,number2) Returns
the greater of number1 and number2.
-
min(number1,number2) Returns
the smaller of number1 and number2.
-
pow(number1,number2) Returns
the value of number1 to the power of number2.
-
random() Returns a random number
between zero and one (at press time, this method only was available on
UNIX versions of Navigator 2.0).
-
round(number) Returns
the closest integer to number[md]in other words rounds to
the closest integer.
-
sin(number) Returns the sine
of number where number represents an angle
in radians.
-
sqrt(number) Returns
the square root of number.
-
tan(number) Returns the tangent
of number where number represents an angle
in radians.
The navigator
object
The navigator object reflects information about the version of Navigator
being used.
Properties
-
appCodeName A string value containing
the code name of the client (i.e. "Mozilla" for Netscape Navigator).
-
appName A string value containing
the name of the client (i.e. "Netscape" for Netscape Navigator).
-
appVersion A string value containing
the version information for the client in the form
versionNumber (platform; country)
For instance, Navigator 2.0, beta 6 for Windows 95 (international version),
would have an appVersion property with the value "2.0b6 (Win32;
I)".
-
userAgent A string containing
the complete value of the user-agent header sent in the HTTP request. This
contains all the information in appCodeName and appVersion:
Mozilla/2.0b6 (Win32; I)
The password
Object
The password object reflects a password text field from an HTML
form in JavaScript.
Properties
-
defaultValue A string value
containing the default value of the password element (i.e. the value of
the VALUE attribute).
-
name A string value containing
the name of the password element.
-
value A string value containing
the value of the password element.
Methods
-
focus() Emulates the action
of focusing in the password field.
-
blur() Emulates the action of
removing focus from the password field.
-
select() Emulates the action
of selecting the text in the password field.
The radio
Object
The radio object reflects a set of radio buttons from an HTML form
in JavaScript. To access individual radio buttons, use numeric indexes
starting at zero. For instance, individual buttons in a set of radio buttons
named testRadio could be referenced by testRadio[0], testRadio[1],
etc.
Properties
-
checked A boolean value indicating
if a specific button is checked. Can be used to select or deselect a button.
-
defaultChecked A boolean value
indicating if a specific button was checked by default (i.e. reflects the
CHECKED attribute).
-
length An integer value indicating
the number of radio buttons in the set.
-
name A string value containing
the name of the set of radio buttons.
-
value A string value containing
the value a specific radio button in a set (i.e. reflects the VALUE
attribute).
Methods
-
click() Emulates the action
of clicking on a radio button.
Event Handlers
-
onClick Specifies JavaScript
code to execute when a radio button is clicked.
The reset
Object
The reset object reflects a reset button from an HTML form in JavaScript.
Properties
-
name A string value containing
the name of the reset element.
-
value A string value containing
the value of the reset element.
Methods
-
click() Emulates the action
of clicking on the reset button.
Event Handlers
-
onClick Specifies JavaScript
code to execute when the reset button is clicked.
The select
Object
The select object reflects a selection list from an HTML form in
JavaScript.
Properties
-
length An integer value containing
the number of options in the selection list.
-
name A string value containing
the name of the selection list.
-
options An array reflecting
each of the options in the selection list in the order they appear. The
options property has it's own properties:
defaultSelected
|
A boolean value indicating if an option was selected by default (i.e. reflects the SELECTED attribute).
|
index
|
An integer value reflecting the index of an option.
|
length
|
An integer value reflecting the number of options in the selection list.
|
name
|
A string value containing the name of the selection list.
|
options
|
A string value containing the full HTML code for the selection list.
|
selected
|
A boolean value indicating if the option is selected. Can be used to select or deselect an option.
|
selectedIndex
|
An integer value containing the index of the currently selected option.
|
text
|
A string value containing the text displayed in the selection list for a particular option.
|
value
|
A string value indicating the value for the specified option (i.e. reflects the VALUE attribute).
|
-
selectedIndex Reflects the index
of the currently selected option in the selection list.
Event Handlers
-
onBlur Specifies JavaScript
code to execute when the selection list loses focus.
-
onFocus Specifies JavaScript
code to execute when focus is given to the selection list.
-
onChange Specifies JavaScript
code to execute when the selected option in the list changes.
The string
Object
The string object provides properties and methods for working with
string literals and variables.
Properties
-
length An integer value containing
the length of the string expressed as the number of characters in the string.
Methods
-
anchor(name) Returns
a string containing the value of the string object surrounded by an A
container tag with the NAME attribute set to name.
-
big() Returns a string containing
the value of the string object surrounded by a BIG container tag.
-
blink() Returns a string containing
the value of the string object surrounded by a BLINK container tag.
-
bold() Returns a string containing
the value of the string object surrounded by a B container tag.
-
charAt(index) Returns
the character at the location specified by index.
-
fixed() Returns a string containing
the value of the string object surrounded by a FIXED container tag.
-
fontColor(color) Returns
a string containing the value of the string object surrounded by a FONT
container tag with the COLOR attribute set to color
where color is a color name or an RGB triplet.
-
fontSize(size) Returns
a string containing the value of the string object surrounded by a FONTSIZE
container tag with the size set to size.
-
indexOf(findString,startingIndex)
Returns the index of the first occurrence of findString,
starting the search at startingIndex where startingIndex
is optional[md]if it is not provided, the search starts at the start of
the string.
-
italics() Returns a string containing
the value of the string object surrounded by an I container tag.
-
lastIndexOf(findString,startingIndex)
Returns the index of the last occurrence of findString. This
is done by searching backwards from startingIndex. startingIndex
is optional and assumed to be the last character in the string if no value
is provided.
-
link(href) Returns a
string containing the value of the string object surrounded by an A
container tag with the HREF attribute set to href.
-
small() Returns a string containing
the value of the string object surrounded by a SMALL container tag.
-
strike() Returns a string containing
the value of the string object surrounded by a STRIKE container
tag.
-
sub() Returns a string containing
the value of the string object surrounded by a SUB container tag.
-
substring(firstIndex,lastIndex)
Returns a string equivalent to the substring starting at firstIndex
and ending at the character before lastIndex. If firstIndex
is greater than lastIndex, the string starts at lastIndex
and ends at the character before firstIndex.
-
sup() Returns a string containing
the value of the string object surrounded by a SUP container tag.
-
toLowerCase() Returns a string
containing the value of the string object with all character converted
to lower case.
-
toUpperCase() Returns a string
containing the value of the string object with all character converted
to upper case.
The submit
Object
The submit object reflects a submit button from an HTML form in
JavaScript.
Properties
-
name A string value containing
the name of the submit button element.
-
value A string value containing
the value of the submit button element.
Methods
-
click() Emulates the action
of clicking on the submit button.
Event Handlers
-
onClick Specifies JavaScript
code to execute when the submit button is clicked.
The text
Object
The text object reflects a text field from an HTML form in JavaScript.
Properties
-
defaultValue A string value
containing the default value of the text element (i.e. the value of the
VALUE attribute).
-
name A string value containing
the name of the text element.
-
value A string value containing
the value of the text element.
Methods
-
focus() Emulates the action
of focusing in the text field.
-
blur() Emulates the action of
removing focus from the text field.
-
select() Emulates the action
of selecting the text in the text field.
Event Handlers
-
onBlur Specifies JavaScript
code to execute when focus is removed from the field.
-
onChange Specifies JavaScript
code to execute when the content of the field is changed.
-
onFocus Specifies JavaScript
code to execute when focus is given to the field.
-
onSelect Specifies JavaScript
code to execute when the user selects some or all of the text in the field.
The textarea
Object
The textarea object reflects a multi-line text field from an HTML
form in JavaScript.
Properties
-
defaultValue A string value
containing the default value of the textarea element (i.e. the value of
the VALUE attribute).
-
name A string value containing
the name of the textarea element.
-
value A string value containing
the value of the textarea element.
Methods
-
focus() Emulates the action
of focusing in the textarea field.
-
blur() Emulates the action of
removing focus from the textarea field.
-
select() Emulates the action
of selecting the text in the textarea field.
Event Handlers
-
onBlur Specifies JavaScript
code to execute when focus is removed from the field.
-
onChange Specifies JavaScript
code to execute when the content of the field is changed.
-
onFocus Specifies JavaScript
code to execute when focus is given to the field.
-
onSelect Specifies JavaScript
code to execute when the user selects some or all of the text in the field.
The window
Object
The window object is the top-level object for each window or frame
and is the parent object for the document, location and history objects.
Properties
-
defaultStatus A string value
containing the default value displayed in the status bar.
-
frames An array of objects for
each frame in a window. Frames appear in the array in the order in which
they appear in the HTML source code.
-
length An integer value indicating
the number of frames in a parent window.
-
name A string value containing
the name of the window or frame.
-
parent A string indicating the
name of the window containing the frameset.
-
self A alternative for the name
of the current window.
-
status Used to display a message
in the status bar[md]this is done by assigning values to this property.
-
top An alternative for the name
of the top-most window.
-
window An alternative for the
name of the current window.
Methods
-
alert(message) Displays
message in a dialog box.
-
close() Closes the window.
-
confirm(message) Displays
message in a dialog box with OK and CANCEL buttons. Returns
true or false based on the button clicked by the user.
-
open(url,name,features) Opens
url in a window named name. If name
doesn't exist, a new window is created with that name. features
is an optional string argument containing a list of features for the new
window. The feature list contains any of the following name-value pairs
separated by commas and without additional spaces:
toolbar=[yes,no,1,0]
|
Indicates if the window should have a toolbar
|
location=[yes,no,1,0]
|
Indicates if the window should have a location field
|
directories=[yes,no,1,0]
|
Indicates if the window should have directory buttons
|
status=[yes,no,1,0]
|
Indicates if the window should have a status bar
|
menubar=[yes,no,1,0]
|
Indicates if the window should have menus
|
scrollbars=[yes,no,1,0]
|
Indicates if the window should have scroll bars
|
resizable=[yes,no,1,0]
|
Indicates if the window should be resizable
|
width=pixels
|
Indicates the width of the window in pixels
|
height=pixels
|
Indicates the height of the window in pixels
|
-
prompt(message,response) Displays
message in a dialog box with a text entry field with the
default value of response. The user's response in the text entry
field is returned as a string.
-
setTimeout(expression,time)
Evaluates expression after time where time
is a value in milliseconds. The time out can be named with the structure
name = setTimeOut(expression,time)
-
clearTimeout(name) Cancels
the time out with the name name.
Event Handlers
-
onLoad Specifies JavaScript
code to execute when the window or frame finishes loading.
-
onUnload Specifies JavaScript
code to execute when the document in the window or frame is exited.
Independent
Functions, Operators, Variables, and Literals
Independent
Functions
-
escape(character) Returns a
string containing the ASCII encoding of character in the
form %xx where xx is the numeric encoding of the character.
-
eval(expression) Returns the
result of evaluating expression where expression
is an arithmetic expression.
-
isNaN(value) Evaluates
value to see if it is NaN. Returns a boolean value. This function
is only available on UNIX platforms where certain functions return NaN
if their argument is not a number.
-
parseFloat(string) Converts
string to a floating point number and returns the value.
It continues to convert until it hits a non-numeric character and then
returns the result. If the first character cannot be converted to a number
the function returns "NaN" (zero on Windows platforms).
-
parseInt(string,base)
Converts string to an integer of base base
and returns the value. It continues to convert until it hits a non-numeric
character and then returns the result. If the first character cannot be
converted to a number, the function returns "NaN" (zero on Windows
platforms).
-
unescape(string) Returns
a character based on the ASCII encoding contained in string.
The ASCII encoding should take the form "%integer" or "hexadecimalValue".
Operators
-
Assignment Operators Table B.1.
Assignment operators in JavaScript
Table B.1. Assignment operators.
Operator
|
Description
|
=
|
Assigns value of right operand to the left operand
|
+=
|
Adds the left and right operands and assigns the result to the left operand
|
-=
|
Subtracts the right operand from the left operand and assigns the result to the left operand
|
*=
|
Multiplies the two operands and assigns the result to the left operand
|
/=
|
Divides the left operand by the right operand and assigns the value to the left operand
|
%=
|
Divides the left operand by the right operand and assigns the remainder to the left operand
|
-
Arithmetic Operators Table B.2.
Arithmetic operators in JavaScript
Table B.2. Arithmetic operators.
Operator
|
Description
|
+
|
Adds the left and right operands
|
-
|
Subtracts the right operand from the left operand
|
*
|
Multiplies the two operands
|
/
|
Divides the left operand by the right operand
|
%
|
Divides the left operand by the right operand and evaluates to the remainder
|
++
|
Increments the operand by one (can be used before or after the operand)
|
--
|
Decreases the operand by one (can be used before or after the operand)
|
-
|
Changes the sign of the operand
|
-
Bitwise Operators Bitwise operators
deal with their operands as binary numbers but return JavaScript numerical
value (see Table B.3).
Table B.3. Bitwise Operators in JavaScript.
Operator
|
Description
|
AND (or &)
|
Converts operands to integers with 32 bits, pairs the corresponding bits and returns one for each pair of ones. Returns zero for any other combination
|
OR (or |)
|
Converts operands to integers with 32 bits, pairs the corresponding bits and returns one for each pair where one of the two bits is one. Returns zero if both bits are zero
|
XOR (or ^)
|
Converts operands to integer with 32 bits, pairs the corresponding bits and returns one for each pair where only one bit is one. Returns zero for any other combination.
|
<<
|
Converts the left operand to an integer with 32 bits and shifts bits to the left the number of bits indicated by the right operand[md]bits shifted off to the left are discarded and zeros are shifted in from the right
|
>>>
|
Converts the left operand to an integer with 32 bits and shifts bits to the right the number of bits indicated by the right operand[md]bits shifted off to the right are discarded and zeros are shifted in from the left
|
>>
|
Converts the left operand to an integer with 32 bits and shifts bits to the right the number of bits indicated by the right operand[md]bits shifted off to the right are discarded and copies of the leftmost bit are shifted in from the left
|
-
Logical Operators Table B.4.
Logical operators in JavaScript
Table B.4. Logical operators.
Operator
|
Description
|
&&
|
Logical "and"[md]returns true when both operands are true, otherwise it returns false
|
||
|
Logical "or"[md]returns true if either operand is true. It only returns false when both operands are false
|
!
|
Logical "not"[md]returns true if the operand is false and false if the operand is true. This is a unary operator and precedes the operand.
|
-
Logical Operators Table B.5.
Comparison Operators in JavaScript
Table B.5. Logical (comparison) operators.
Operator
|
Description
|
==
|
Returns true if the operands are equal
|
!=
|
Returns true if the operands are not equal
|
>
|
Returns true if the left operand is greater than the right operand
|
<
|
Returns true if the left operand is less than the right operand
|
>=
|
Returns true if the left operand is greater than or equal to the right operand
|
<=
|
Returns true if the left operand is less than or equal to the right operand
|
-
Conditional Operators Conditional
expressions take one form:
(condition) ? val1 : val2
If condition is true, the expression evaluates to val1,
otherwise it evaluates to val2.
-
String Operators The concatenation
operators (+) is one of two string operators. It evaluates to a string
combining the left and right operands. The concatenation assignment operator
(+=) is also available.
-
Operator Precedence JavaScript
applies the rules of operator precedence as follows (from lowest to highest
precedence):
comma (,)
assignment operators (= += -= *= /= %=)
conditional (? :)
logical or (||)
logical and (&&)
bitwise or (|)
bitwise xor (^)
bitwise and (&)
equality (== !=)
relational (< <= > >=)
shift (<< >> >>>)
addition/subtraction (+ -)
multiply/divide/modulus (* / %)
negation/increment (! - ++ --)
call, member (() [])