JavaScript 1.0: Create a
JavaScript 1.1, NES 2.0: added
JavaScript 1.2, NES 3.0: added
JavaScript 1.3: added | |
String
constructor:
new String(string)
string |
String
object is a wrapper around the string primitive data type. Do not confuse a string literal with the String
object. For example, the following code creates the string literal s1
and also the String
object s2
:
s1 = "foo" // creates a string literal valueYou can call any of the methods of the
s2 = new String("foo") // creates a String object
String
object on a string literal value--JavaScript automatically converts the string literal to a temporary String
object, calls the method, then discards the temporary String
object. You can also use the String.length
property with a string literal.
You should use string literals unless you specifically need to use a String
object, because String
objects can have counterintuitive behavior. For example:
s1 = "2 + 2" // creates a string literal valueA string can be represented as a literal enclosed by single or double quotation marks; for example, "Netscape" or `Netscape'. You can convert the value of any object into a string using the top-level
s2 = new String("2 + 2") // creates a String object
eval(s1) // returns the number 4
eval(s2) // returns the string "2 + 2"
String
function.
Property |
Description
|
|
| |
---|
watch
and unwatch
methods from Object
.
var last_name = "Schaefer"Example 2: String literal properties. The following statements evaluate to 8,
"SCHAEFER,"
and "schaefer"
:
last_name.lengthExample 3: Accessing individual characters in a string. You can think of a string as an array of characters. In this way, you can access the individual characters in the string by indexing that array. For example, the following code displays "The first character in the string is H":
last_name.toUpperCase()
last_name.toLowerCase()
var myString = "Hello"Example 4: Pass a string among scripts in different windows or frames. The following code creates two string variables and opens a second window:
myString[0] // returns "H"
var lastName = "Schaefer"If the HTML source for the second window (
var firstName = "Jesse"
empWindow=window.open('string2.html','window1','width=300,height=300')
string2.html
) creates two string variables, empLastName
and empFirstName
, the following code in the first window assigns values to the second window's variables:
empWindow.empFirstName=firstNameThe following code in the first window displays the values of the second window's variables:
empWindow.empLastName=lastName
alert('empFirstName in empWindow is ' + empWindow.empFirstName)
alert('empLastName in empWindow is ' + empWindow.empLastName)
anchor(nameAttribute)
nameAttribute |
anchor
method with the document.write
or document.writeln
methods to programmatically create and display an anchor in a document. Create the anchor with the anchor
method, and then call write
or writeln
to display the anchor in a document. In server-side JavaScript, use the write
function to display the anchor.
In the syntax, the text
string represents the literal text that you want the user to see. The nameAttribute
string represents the NAME
attribute of the A
tag.
Anchors created with the anchor
method become elements in the document.anchors
array.
msgWindow
window and creates an anchor for the table of contents:
var myString="Table of Contents"The previous example produces the same output as the following HTML:
msgWindow.document.writeln(myString.anchor("contents_anchor"))
<A NAME="contents_anchor">Table of Contents</A>
String.link
BIG
tag.big()
big
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to display the string.
string
methods to change the size of a string:
var worldString="Hello, world"
document.write(worldString.small())The previous example produces the same output as the following HTML:
document.write("<P>" + worldString.big())
document.write("<P>" + worldString.fontsize(7))
<SMALL>Hello, world</SMALL>
<P><BIG>Hello, world</BIG>
<P><FONTSIZE=7>Hello, world</FONTSIZE>
String.fontsize
, String.small
BLINK
tag.blink()
blink
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to display the string.
string
methods to change the formatting of a string:
var worldString="Hello, world"
document.write(worldString.blink())The previous example produces the same output as the following HTML:
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())
<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>
String.bold
, String.italics
, String.strike
B
tag.bold()
bold
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to display the string.
string
methods to change the formatting of a string:
var worldString="Hello, world"The previous example produces the same output as the following HTML:
document.write(worldString.blink())
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())
<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>
String.blink
, String.italics
, String.strike
charAt(index)
index | An integer between 0 and 1 less than the length of the string. |
stringName
is stringName.length - 1
. If the index
you supply is out of range, JavaScript returns an empty string.
"Brave new world"
:
var anyString="Brave new world"
document.writeln("The character at index 0 is " + anyString.charAt(0))These lines display the following: The character at index 0 is B
document.writeln("The character at index 1 is " + anyString.charAt(1))
document.writeln("The character at index 2 is " + anyString.charAt(2))
document.writeln("The character at index 3 is " + anyString.charAt(3))
document.writeln("The character at index 4 is " + anyString.charAt(4))
String.indexOf
, String.lastIndexOf
, String.split
JavaScript 1.3: returns a Unicode value rather than an ISO-Latin-1 value | |
charCodeAt([index])
index | An integer between 0 and 1 less than the length of the string. The default value is 0. |
charCodeAt
method returns a number indicating the ISO-Latin-1 codeset value of the character at the given index. The ISO-Latin-1 codeset ranges from 0 to 255. The first 0 to 127 are a direct match of the ASCII character set.
"ABC".charCodeAt(0) // returns 65Example 2. The following example enables the creation of an event used to simulate a key press. A KeyPress event has a
which
property that represents the ASCII value of the pressed key. If you know the letter, number, or symbol, you can use charCodeAt
to supply the ASCII value to which
.
//create an event object with appropriate property values
ev = new Event()
ev.type = KeyPress
ev.layerX = 150
//assign values to layerY, pageX, pageY, screenX, and screenY
...
//assign the ASCII value to the which property
ev.which = "v".charCodeAt(0)
//assign modifier property
ev.modifiers = <FONT COLOR="#FF0080">How do I do this?</FONT>
concat(string2, string3[, ..., stringN])
string2... |
concat
combines the text from two strings and returns a new string. Changes to the text in one string do not affect the other string.
s1="Oh "
s2="what a beautiful "
s3="mornin'."
s4=s1.concat(s2,s3) // returns "Oh what a beautiful mornin'."
Object.constructor
.
TT
tag.fixed()
fixed
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to display the string.
fixed
method to change the formatting of a string:
var worldString="Hello, world"The previous example produces the same output as the following HTML:
document.write(worldString.fixed())
<TT>Hello, world</TT>
<FONT COLOR=color>
tag.fontcolor(color)
color | A string expressing the color as a hexadecimal RGB triplet or as a string literal. String literals for color names are listed in the Client-Side JavaScript Guide. |
fontcolor
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to display the string.
If you express 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 fontcolor
method overrides a value set in the fgColor
property.
fontcolor
method to change the color of a string:
var worldString="Hello, world"
document.write(worldString.fontcolor("maroon") +
" is maroon in this line")
document.write("<P>" + worldString.fontcolor("salmon") +
" is salmon in this line")
document.write("<P>" + worldString.fontcolor("red") +
" is red in this line")
document.write("<P>" + worldString.fontcolor("8000") +The previous example produces the same output as the following HTML:
" is maroon in hexadecimal in this line")
document.write("<P>" + worldString.fontcolor("FA8072") +
" is salmon in hexadecimal in this line")
document.write("<P>" + worldString.fontcolor("FF00") +
" is red in hexadecimal in this line")
<FONT COLOR="maroon">Hello, world</FONT> is maroon in this line
<P><FONT COLOR="salmon">Hello, world</FONT> is salmon in this line
<P><FONT COLOR="red">Hello, world</FONT> is red in this line
<FONT COLOR="8000">Hello, world</FONT>
is maroon in hexadecimal in this line
<P><FONT COLOR="FA8072">Hello, world</FONT>
is salmon in hexadecimal in this line
<P><FONT COLOR="FF00">Hello, world</FONT>
is red in hexadecimal in this line
<FONT SIZE=size>
tag.fontsize(size)
size | An integer between 1 and 7, a string representing a signed integer between 1 and 7. |
fontsize
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to display the string.
When you specify size
as an integer, you set the size of stringName
to one of the 7 defined sizes. When you specify size
as a string such as "-2"
, you adjust the font size of stringName
relative to the size set in the BASEFONT
tag.
string
methods to change the size of a string:
var worldString="Hello, world"
document.write(worldString.small())The previous example produces the same output as the following HTML:
document.write("<P>" + worldString.big())
document.write("<P>" + worldString.fontsize(7))
<SMALL>Hello, world</SMALL>
<P><BIG>Hello, world</BIG>
<P><FONTSIZE=7>Hello, world</FONTSIZE>
String.big
, String.small
JavaScript 1.3: uses a Unicode value rather than an ISO-Latin-1 value | |
fromCharCode(num1, ..., numN)
num1, ..., numN |
String
object.
Because fromCharCode
is a static method of String
, you always use it as String.fromCharCode()
, rather than as a method of a String
object you created.
fromCharCode
method returns a string created by using the specified sequence of ISO-Latin-1 codeset values.
String.fromCharCode(65,66,67)Example 2. The
which
property of the KeyDown
, KeyPress
, and KeyUp
events contains the ASCII value of the key pressed at the time the event occurred. If you want to get the actual letter, number, or symbol of the key, you can use fromCharCode
. The following example returns the letter, number, or symbol of the KeyPress event's which
property.
String.fromCharCode(KeyPress.which)
String
object of the first occurrence of the specified value, starting the search at fromIndex
, or -1 if the value is not found.indexOf(searchValue[, fromIndex])
searchValue | |
fromIndex |
stringName
is stringName.length - 1
.
"Blue Whale".indexOf("Blue") // returns 0The
"Blue Whale".indexOf("Blute") // returns -1
"Blue Whale".indexOf("Whale",0) // returns 5
"Blue Whale".indexOf("Whale",5) // returns 5
"Blue Whale".indexOf("",9) // returns 9
"Blue Whale".indexOf("",10) // returns 10
"Blue Whale".indexOf("",11) // returns 10
indexOf
method is case sensitive. For example, the following expression returns -1:
"Blue Whale".indexOf("blue")
indexOf
and lastIndexOf
to locate values in the string "Brave new world."
var anyString="Brave new world"
// Displays 8Example 2. The following example defines two string variables. The variables contain the same string except that the second string contains uppercase letters. The first
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"))
writeln
method displays 19. But because the indexOf
method is case sensitive, the string "cheddar"
is not found in myCapString
, so the second writeln
method displays -1.
myString="brie, pepper jack, cheddar"Example 3. The following example sets
myCapString="Brie, Pepper Jack, Cheddar"
document.writeln('myString.indexOf("cheddar") is ' +
myString.indexOf("cheddar"))
document.writeln('<P>myCapString.indexOf("cheddar") is ' +
myCapString.indexOf("cheddar"))
count
to the number of occurrences of the letter x
in the string str
:
count = 0;
pos = str.indexOf("x");
while ( pos != -1 ) {
count++;
pos = str.indexOf("x",pos+1);
}
String.charAt
, String.lastIndexOf
, String.split
I
> tag.italics()
italics
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to display the string.
string
methods to change the formatting of a string:
var worldString="Hello, world"
document.write(worldString.blink())The previous example produces the same output as the following HTML:
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())
<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>
String.blink
, String.bold
, String.strike
String
object of the last occurrence of the specified value, or -1 if not found. The calling string is searched backward, starting at fromIndex
.lastIndexOf(searchValue[, fromIndex])
searchValue | |
fromIndex |
stringName
.length - 1.
"canal".lastIndexOf("a") // returns 3The
"canal".lastIndexOf("a",2) // returns 1
"canal".lastIndexOf("a",0) // returns -1
"canal".lastIndexOf("x") // returns -1
lastIndexOf
method is case sensitive. For example, the following expression returns -1:
"Blue Whale, Killer Whale".lastIndexOf("blue")
indexOf
and lastIndexOf
to locate values in the string "Brave new world."
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"))
String.charAt
, String.indexOf
, String.split
var x="Netscape"
alert("The string length is " + x.length)
link(hrefAttribute)
hrefAttribute |
link
method to programmatically create a hypertext link, and then call write
or writeln
to display the link in a document. In server-side JavaScript, use the write
function to display the link.
Links created with the link
method become elements in the links
array of the document
object. See document.links
.
var hotText="Netscape"
var URL="http://home.netscape.com"
document.write("Click to return to " + hotText.link(URL))The previous example produces the same output as the following HTML:
Click to return to <A HREF="http://home.netscape.com">Netscape</A>
Anchor
match(regexp)
regexp | Name of the regular expression. It can be a variable name or a literal. |
g
(for global) and i
(for ignore case) flags in the regular expression. These can be included separately or together. The following two examples below show how to use these flags with match
.
NOTE: If you execute a match simply to find true or false, useString.search
or the regular expressiontest
method.
match
is used to find 'Chapter' followed by 1 or more numeric characters followed by a decimal point and numeric character 0 or more times. The regular expression includes the i
flag so that case will be ignored.
<SCRIPT>This returns the array containing Chapter 3.4.5.1,Chapter 3.4.5.1,.1
str = "For more information, see Chapter 3.4.5.1";
re = /(chapter \d+(\.\d)*)/i;
found = str.match(re);
document.write(found);
</SCRIPT>
'Chapter 3.4.5.1'
is the first match and the first value remembered from (Chapter \d+(\.\d)*)
.
'.1'
is the second value remembered from (\.\d)
.
Example 2. The following example demonstrates the use of the global and ignore case flags with match
.
<SCRIPT>The returned array contains D, d.
str = "abcDdcba";
newArray = str.match(/d/gi);
document.write(newArray);
</SCRIPT>
Function.prototype
.JavaScript 1.3: supports the nesting of a function in place of the second argument |
replace(regexp, newSubStr)Versions prior to JavaScript 1.3:
replace(regexp, function)
replace(regexp, newSubStr)
String
object it is called on; it simply returns a new string.
If you want to execute a global search and replace, or a case insensitive search, include the g
(for global) and i
(for ignore case) flags in the regular expression. These can be included separately or together. The following two examples below show how to use these flags with replace
.
Specifying a function as a parameter.
When you specify a function as the second parameter, the function is invoked after the match has been performed. (The use of a function in this manner is often called a lambda expression.)
In your function, you can dynamically generate the string that replaces the matched substring. The result of the function call is used as the replacement value.
The nested function can use the matched substrings to determine the new string (newSubStr
) that replaces the found substring. You get the matched substrings through the parameters of your function. The first parameter of your function holds the complete matched substring. Other parameters can be used for parenthetical matches, remembered submatch strings. For example, the following replace
method returns XX.zzzz - XX , zzzz.
"XXzzzz".replace(/(X*)(z*)/,The array returned from the
function (str, p1, p2) {
return str + " - " + p1 + " , " + p2;
}
)
exec
method of the RegExp
object and the subsequent match is available to your function. You can use the content of the array plus the input
and the index
(index of match in the input string) properties of the array to perform additional tasks before the method replaces the substring.
replace
to replace each occurrence of 'apples' in the string with 'oranges.'
<SCRIPT>This prints "oranges are round, and oranges are juicy." Example 2. In the following example, the regular expression is defined in
re = /apples/gi;
str = "Apples are round, and apples are juicy.";
newstr=str.replace(re, "oranges");
document.write(newstr)
</SCRIPT>
replace
and includes the ignore case flag.
<SCRIPT>This prints "Twas the night before Christmas..." Example 3. The following script switches the words in the string. For the replacement text, the script uses the values of the
str = "Twas the night before Xmas...";
newstr=str.replace(/xmas/i, "Christmas");
document.write(newstr)
</SCRIPT>
$1
and $2
properties.
<SCRIPT LANGUAGE="JavaScript1.2">This prints "Smith, John". Example 4. The following example replaces a Fahrenheit degree with its equivalent Celsius degree. The Fahrenheit degree should be a number ending with F. The function returns the Celsius number ending with C. For example, if the input number is 212F, the function returns 100C. If the number is 0F, the function returns -17.77777777777778C. The regular expression
re = /(\w+)\s(\w+)/;
str = "John Smith";
newstr = str.replace(re, "$2, $1");
document.write(newstr)
</SCRIPT>
test
checks for any number that ends with F. The number of Fahrenheit degree is accessible to your function through the parameter $1
. The function sets the Celsius number based on the Fahrenheit degree passed in a string to the f2c
function. f2c
then returns the Celsius number. This function approximates Perl's s///e flag.
function f2c(x) {
var s = String(x)
var test = /(\d+(\.\d*)?)F\b/g
return s.replace
(test,
myfunction ($0,$1,$2) {
return (($1-32) * 5/9) + "C";
}
)
}
String
object. search(regexp)
regexp | Name of the regular expression. It can be a variable name or a literal. |
search
returns the index of the regular expression inside the string. Otherwise, it returns -1.
When you want to know whether a pattern is found in a string use search
(similar to the regular expression test
method); for more information (but slower execution) use match
(similar to the regular expression exec
method).
function testinput(re, str){
if (str.search(re) != -1)
midstring = " contains ";
else
midstring = " does not contain ";
document.write (str + midstring + re.source);
}
slice(beginslice[, endSlice])
beginSlice | |
endSlice |
slice
extracts the text from one string and returns a new string. Changes to the text in one string do not affect the other string.
slice
extracts up to but not including endSlice
. string.slice(1,4)
extracts the second character through the fourth character (characters indexed 1, 2, and 3).
As a negative index, endSlice
indicates an offset from the end of the string. string.slice(2,-1)
extracts the third character through the second to last character in the string.
slice
to create a new string.
<SCRIPT>This writes: morning is upon
str1="The morning is upon us. "
str2=str1.slice(3,-5)
document.write(str2)
</SCRIPT>
SMALL
> tag.small()
small
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to display the string.
string
methods to change the size of a string:
var worldString="Hello, world"
document.write(worldString.small())The previous example produces the same output as the following HTML:
document.write("<P>" + worldString.big())
document.write("<P>" + worldString.fontsize(7))
<SMALL>Hello, world</SMALL>
<P><BIG>Hello, world</BIG>
<P><FONTSIZE=7>Hello, world</FONTSIZE>
String.big
, String.fontsize
String
object into an array of strings by separating the string into substrings. split([separator][, limit])
separator | |
limit | Integer specifying a limit on the number of splits to be found. |
split
method returns the new array.
When found, separator
is removed from the string and the substrings are returned in an array. If separator
is omitted, the array contains one element consisting of the entire string.
In JavaScript 1.2, split
has the following additions:
separator
is a regular expression, any included parenthesis cause submatches to be included in the returned array. LANGUAGE="JavaScript1.2"
in the SCRIPT
tag, string.split(" ")
splits on any run of 1 or more white space characters including spaces, tabs, line feeds, and carriage returns. For this behavior, LANGUAGE="JavaScript1.2"
must be specified in the <SCRIPT>
tag.function splitString (stringToSplit,separator) {
arrayOfStrings = stringToSplit.split(separator)
document.write ('<P>The original string is: "' + stringToSplit + '"')
document.write ('<BR>The separator is: "' + separator + '"')
document.write ("<BR>The array has " + arrayOfStrings.length + " elements: ")
for (var i=0; i < arrayOfStrings.length; i++) {
document.write (arrayOfStrings[i] + " / ")
}
}
var tempestString="Oh brave new world that has such people in it."
var monthString="Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec"
var space=" "
var comma=","
splitString(tempestString,space)This example produces the following output:
splitString(tempestString)
splitString(monthString,comma)
The original string is: "Oh brave new world that has such people in it."
The separator is: " "
The array has 10 elements: Oh / brave / new / world / that / has / such / people / in / it. /
The original string is: "Oh brave new world that has such people in it."
The separator is: "undefined"
The array has 1 elements: Oh brave new world that has such people in it. /
The original string is: "Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec"Example 2. Consider the following script:
The separator is: ","
The array has 12 elements: Jan / Feb / Mar / Apr / May / Jun / Jul / Aug / Sep / Oct / Nov / Dec /
<SCRIPT LANGUAGE="JavaScript1.2">Using
str="She sells seashells \nby the\n seashore"
document.write(str + "<BR>")
a=str.split(" ")
document.write(a)
</SCRIPT>
LANGUAGE="JavaScript1.2"
, this script produces
"She", "sells", "seashells", "by", "the", "seashore"Without
LANGUAGE="JavaScript1.2"
, this script splits only on single space characters, producing
"She", "sells", , , , "seashells", "by", , , "the", "seashore"Example 3. In the following example,
split
looks for 0 or more spaces followed by a semicolon followed by 0 or more spaces and, when found, removes the spaces from the string. nameList
is the array returned as a result of split
.
<SCRIPT>This prints two lines; the first line prints the original string, and the second line prints the resulting array. Harry Trump ;Fred Barney; Helen Rigby ; Bill Abel ;Chris Hand
names = "Harry Trump ;Fred Barney; Helen Rigby ; Bill Abel ;Chris Hand ";
document.write (names + "<BR>" + "<BR>");
re = /\s*;\s*/;
nameList = names.split (re);
document.write(nameList);
</SCRIPT>
split
looks for 0 or more spaces in a string and returns the first 3 splits that it finds.
<SCRIPT LANGUAGE="JavaScript1.2">This script displays the following:
myVar = " Hello World. How are you doing? ";
splits = myVar.split(" ", 3);
document.write(splits)
</SCRIPT>
["Hello", "World.", "How"]
String.charAt
, String.indexOf
, String.lastIndexOf
STRIKE
> tag.strike()
strike
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to display the string.
string
methods to change the formatting of a string:
var worldString="Hello, world"
document.write(worldString.blink())The previous example produces the same output as the following HTML:
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())
<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>
String.blink
, String.bold
, String.italics
SUB
> tag.sub()
sub
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to generate the HTML.
sub
and sup
methods to format a string:
var superText="superscript"
var subText="subscript"
document.write("This is what a " + superText.sup() + " looks like.")The previous example produces the same output as the following HTML:
document.write("<P>This is what a " + subText.sub() + " looks like.")
This is what a <SUP>superscript</SUP> looks like.
<P>This is what a <SUB>subscript</SUB> looks like.
String.sup
substr(start[, length])
start | |
length |
start
is a character index. The index of the first character is 0, and the index of the last character is 1 less than the length of the string. substr
begins extracting characters at start
and collects length
number of characters.
If start
is positive and is the length of the string or longer, substr
returns no characters.
If start
is negative, substr
uses it as a character index from the end of the string. If start
is negative and abs(start)
is larger than the length of the string, substr
uses 0 is the start index.
If length
is 0 or negative, substr
returns no characters. If length
is omitted, start
extracts characters to the end of the string.
<SCRIPT LANGUAGE="JavaScript1.2">
str = "abcdefghij"
document.writeln("(1,2): ", str.substr(1,2))
document.writeln("(-2,2): ", str.substr(-2,2))
document.writeln("(1): ", str.substr(1))
document.writeln("(-20, 2): ", str.substr(1,20))
document.writeln("(20, 2): ", str.substr(20,2))
</SCRIPT>This script displays:
(1,2): bc
(-2,2): ij
(1): bcdefghij
(-20, 2): bcdefghij
(20, 2):
substring
String
object. substring(indexA, indexB)
indexA | An integer between 0 and 1 less than the length of the string. |
indexB | An integer between 0 and 1 less than the length of the string. |
substring
extracts characters from indexA
up to but not including indexB
. In particular:
indexA
is less than 0, indexA
is treated as if it were 0. indexB
is greater than stringName.length
, indexB
is treated as if it were stringName.length
. indexA
equals indexB
, substring
returns an empty string. indexB
is omitted, indexA
extracts characters to the end of the string. LANGUAGE="JavaScript1.2"
in the SCRIPT
tag,
In JavaScript 1.2, without LANGUAGE="JavaScript1.2"
in the SCRIPT
tag,
substring
to display characters from the string "Netscape"
:
var anyString="Netscape"
// Displays "Net"Example 2. The following example replaces a substring within a string. It will replace both individual characters and substrings. The function call at the end of the example changes the string
document.write(anyString.substring(0,3))
document.write(anyString.substring(3,0))
// Displays "cap"
document.write(anyString.substring(4,7))
document.write(anyString.substring(7,4))
// Displays "Netscap"
document.write(anyString.substring(0,7))
// Displays "Netscape"
document.write(anyString.substring(0,8))
document.write(anyString.substring(0,10))
"Brave New World"
into "Brave New Web"
.
function replaceString(oldS,newS,fullS) {
// Replaces oldS with newS in the string fullS
for (var i=0; i<fullS.length; i++) {
if (fullS.substring(i,i+oldS.length) == oldS) {
fullS = fullS.substring(0,i)+newS+fullS.substring(i+oldS.length,fullS.length)
}
}
return fullS
}
replaceString("World","Web","Brave New World")Example 3. In JavaScript 1.2, using
LANGUAGE="JavaScript1.2"
, the following script produces a runtime error (out of memory).
<SCRIPT LANGUAGE="JavaScript1.2">Without
str="Netscape"
document.write(str.substring(0,3);
document.write(str.substring(3,0);
</SCRIPT>
LANGUAGE="JavaScript1.2"
, the above script prints the following:
Net Net
In the second write
, the index numbers are swapped.
substr
SUP
> tag.sup()
sup
method with the write
or writeln
methods to format and display a string in a document. In server-side JavaScript, use the write
function to generate the HTML.
sub
and sup
methods to format a string:
var superText="superscript"
var subText="subscript"
document.write("This is what a " + superText.sup() + " looks like.")The previous example produces the same output as the following HTML:
document.write("<P>This is what a " + subText.sub() + " looks like.")
This is what a <SUP>superscript</SUP> looks like.
<P>This is what a <SUB>subscript</SUB> looks like.
String.sub
toLowerCase()
toLowerCase
method returns the value of the string converted to lowercase. toLowerCase
does not affect the value of the string itself.
"alphabet"
:
var upperText="ALPHABET"
document.write(upperText.toLowerCase())
String.toUpperCase
toSource()
toSource
method returns the following values:
function String() {
[native code]
}
String
or string literals, toSource
returns a string representing the source code.
toString()
String
object overrides the toString
method of the Object
object; it does not inherit Object.toString
. For String
objects, the toString
method returns a string representation of the object.
x = new String("Hello world");
alert(x.toString()) // Displays "Hello world"
Object.toString
toUpperCase()
toUpperCase
method returns the value of the string converted to uppercase. toUpperCase
does not affect the value of the string itself.
"ALPHABET"
:
var lowerText="alphabet"
document.write(lowerText.toUpperCase())
String.toLowerCase
valueOf()
valueOf
method of String
returns the primitive value of a String object as a string data type. This value is equivalent to String.toString
.
This method is usually called internally by JavaScript and not explicitly in code.
x = new String("Hello world");
alert(x.valueOf()) // Displays "Hello world"
String.toString
, Object.valueOf
Last Updated: 05/28/99 12:00:25
Any sample code included above is provided for your use on an "AS IS" basis, under the Netscape License Agreement - Terms of Use