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string

JavaScriptSource Staff Jul 24, 2006
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Core JavaScript Reference 1.5





String

An object representing a series of characters in a string.


Core object

Implemented in  

JavaScript 1.0: Create a String object only by quoting characters.

JavaScript 1.1, NES 2.0: added String constructor; added prototype property; added split method; added ability to pass strings among scripts in different windows or frames (in previous releases, you had to add an empty string to another window's string to refer to it).

JavaScript 1.2, NES 3.0: added concat, match, replace, search, slice, and substr methods.

JavaScript 1.3: added toSource method; changed charCodeAt, fromCharCode, and replace methods.  

ECMA version  

ECMA-262  


Created by
The String constructor:

new String(string)


Parameters


string

 

Any string.  


Description
The 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 value
s2 = new String("foo") // creates a String object

You can call any of the methods of the 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 value
s2 = new String("2 + 2") // creates a String object
eval(s1)     // returns the number 4
eval(s2)     // returns the string "2 + 2"

A 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 String function.


Property Summary


Property

Description

constructor

 

Specifies the function that creates an object's prototype.  

length

 

Reflects the length of the string.  

prototype

 

Allows the addition of properties to a String object.  


Method Summary


Method

Description

anchor

 

Creates an HTML anchor that is used as a hypertext target.  

big

 

Causes a string to be displayed in a big font as if it were in a BIG tag.  

blink

 

Causes a string to blink as if it were in a BLINK tag.  

bold

 

Causes a string to be displayed as if it were in a B tag.  

charAt

 

Returns the character at the specified index.  

charCodeAt

 

Returns a number indicating the Unicode value of the character at the given index.  

concat

 

Combines the text of two strings and returns a new string.  

fixed

 

Causes a string to be displayed in fixed-pitch font as if it were in a TT tag.  

fontcolor

 

Causes a string to be displayed in the specified color as if it were in a <FONT COLOR=color> tag.  

fontsize

 

Causes a string to be displayed in the specified font size as if it were in a <FONT SIZE=size> tag.  

fromCharCode

 

Returns a string created by using the specified sequence of Unicode values. This is a method on the String class, not on a String instance.  

indexOf

 

Returns the index within the calling String object of the first occurrence of the specified value, or -1 if not found.  

italics

 

Causes a string to be italic, as if it were in an I tag.  

lastIndexOf

 

Returns the index within the calling String object of the last occurrence of the specified value, or -1 if not found.  

link

 

Creates an HTML hypertext link that requests another URL.  

match

 

Used to match a regular expression against a string.  

replace

 

Used to find a match between a regular expression and a string, and to replace the matched substring with a new substring.  

search

 

Executes the search for a match between a regular expression and a specified string.  

slice

 

Extracts a section of a string and returns a new string.  

small

 

Causes a string to be displayed in a small font, as if it were in a SMALL tag.  

split

 

Splits a String object into an array of strings by separating the string into substrings.  

strike

 

Causes a string to be displayed as struck-out text, as if it were in a STRIKE tag.  

sub

 

Causes a string to be displayed as a subscript, as if it were in a SUB tag.  

substr

 

Returns the characters in a string beginning at the specified location through the specified number of characters.  

substring

 

Returns the characters in a string between two indexes into the string.  

sup

 

Causes a string to be displayed as a superscript, as if it were in a SUP tag.  

toLowerCase

 

Returns the calling string value converted to lowercase.  

toSource

 

Returns an object literal representing the specified object; you can use this value to create a new object. Overrides the Object.toSource method.  

toString

 

Returns a string representing the specified object. Overrides the Object.toString method.  

toUpperCase

 

Returns the calling string value converted to uppercase.  

valueOf

 

Returns the primitive value of the specified object. Overrides the Object.valueOf method.  

In addition, this object inherits the watch and unwatch methods from Object.


Examples
Example 1: String literal. The following statement creates a string literal:

var last_name = "Schaefer"

Example 2: String literal properties. The following statements evaluate to 8, "SCHAEFER," and "schaefer":

last_name.length
last_name.toUpperCase()
last_name.toLowerCase()

Example 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":

var myString = "Hello"
myString[0] // returns "H"

Example 4: Pass a string among scripts in different windows or frames. The following code creates two string variables and opens a second window:

var lastName = "Schaefer"
var firstName = "Jesse"
empWindow=window.open('string2.html','window1','width=300,height=300')

If the HTML source for the second window (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=firstName
empWindow.empLastName=lastName

The following code in the first window displays the values of the second window's variables:

alert('empFirstName in empWindow is ' + empWindow.empFirstName)
alert('empLastName in empWindow is ' + empWindow.empLastName)


anchor

Creates an HTML anchor that is used as a hypertext target.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
anchor(nameAttribute)


Parameters



nameAttribute

 

A string.  


Description
Use the 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.


Examples
The following example opens the msgWindow window and creates an anchor for the table of contents:

var myString="Table of Contents"
msgWindow.document.writeln(myString.anchor("contents_anchor"))

The previous example produces the same output as the following HTML:

<A NAME="contents_anchor">Table of Contents</A>


See also
String.link


big

Causes a string to be displayed in a big font as if it were in a BIG tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
big()


Parameters
None


Description
Use the 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.


Examples
The following example uses string methods to change the size of a string:

var worldString="Hello, world"

document.write(worldString.small())
document.write("<P>" + worldString.big())
document.write("<P>" + worldString.fontsize(7))

The previous example produces the same output as the following HTML:

<SMALL>Hello, world</SMALL>
<P><BIG>Hello, world</BIG>
<P><FONTSIZE=7>Hello, world</FONTSIZE>


See also
String.fontsize, String.small


blink

Causes a string to blink as if it were in a BLINK tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
blink()


Parameters
None


Description
Use the 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.


Examples
The following example uses string methods to change the formatting of a string:

var worldString="Hello, world"

document.write(worldString.blink())
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())

The previous example produces the same output as the following HTML:

<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>


See also
String.bold, String.italics, String.strike


bold

Causes a string to be displayed as bold as if it were in a B tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
bold()


Parameters
None


Description
Use the 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.


Examples
The following example uses string methods to change the formatting of a string:

var worldString="Hello, world"
document.write(worldString.blink())
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())

The previous example produces the same output as the following HTML:

<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>


See also
String.blink, String.italics, String.strike


charAt

Returns the specified character from the string.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  

ECMA version  

ECMA-262  


Syntax
charAt(index)


Parameters



index

 

An integer between 0 and 1 less than the length of the string.  


Description
Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character in a string called stringName is stringName.length - 1. If the index you supply is out of range, JavaScript returns an empty string.


Examples
The following example displays characters at different locations in the string "Brave new world":

var anyString="Brave new world"

document.writeln("The character at index 0 is " + anyString.charAt(0))
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))

These lines display the following:

The character at index 0 is B
The character at index 1 is r
The character at index 2 is a
The character at index 3 is v
The character at index 4 is e


See also
String.indexOf, String.lastIndexOf, String.split


charCodeAt

Returns a number indicating the Unicode value of the character at the given index.



Method of  

String  

Implemented in  

JavaScript 1.2, NES 3.0

JavaScript 1.3: returns a Unicode value rather than an ISO-Latin-1 value.  

ECMA version  

ECMA-262  


Syntax
charCodeAt([index])


Parameters



index

 

An integer between 0 and 1 less than the length of the string. The default value is 0.  


Description
Unicode values range from 0 to 65,535. The first 128 Unicode values are a direct match of the ASCII character set. For information on Unicode, see the Core JavaScript Guide.


Backward Compatibility

JavaScript 1.2. The 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.


Example
The following example returns 65, the Unicode value for A.

"ABC".charCodeAt(0) // returns 65


concat

Combines the text of two or more strings and returns a new string.



Method of  

String  

Implemented in  

JavaScript 1.2, NES 3.0  


Syntax
concat(string2, string3[, ..., stringN])


Parameters



string2...
stringN

 

Strings to concatenate to this string.  


Description
concat combines the text from one or more strings and returns a new string. Changes to the text in one string do not affect the other string.


Example
The following example combines two strings into a new string.

s1="Oh "
s2="what a beautiful "
s3="mornin'."
s4=s1.concat(s2,s3) // returns "Oh what a beautiful mornin'."


constructor

Specifies the function that creates an object's prototype. Note that the value of this property is a reference to the function itself, not a string containing the function's name.



Property of  

String  

Implemented in  

JavaScript 1.1, NES 2.0  

ECMA version  

ECMA-262  


Description
See Object.constructor.


fixed

Causes a string to be displayed in fixed-pitch font as if it were in a TT tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
fixed()


Parameters
None


Description
Use the 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.


Examples
The following example uses the fixed method to change the formatting of a string:

var worldString="Hello, world"
document.write(worldString.fixed())

The previous example produces the same output as the following HTML:

<TT>Hello, world</TT>


fontcolor

Causes a string to be displayed in the specified color as if it were in a <FONT COLOR=color> tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
fontcolor(color)


Parameters



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 Core JavaScript Guide.  


Description
Use the 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.


Examples
The following example uses the 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") +
   " 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")

The previous example produces the same output as the following HTML:

<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


fontsize

Causes a string to be displayed in the specified font size as if it were in a <FONT SIZE=size> tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
fontsize(size)


Parameters



size

 

An integer between 1 and 7, a string representing a signed integer between 1 and 7.  


Description
Use the 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.


Examples
The following example uses string methods to change the size of a string:

var worldString="Hello, world"

document.write(worldString.small())
document.write("<P>" + worldString.big())
document.write("<P>" + worldString.fontsize(7))

The previous example produces the same output as the following HTML:

<SMALL>Hello, world</SMALL>
<P><BIG>Hello, world</BIG>
<P><FONTSIZE=7>Hello, world</FONTSIZE>


See also
String.big, String.small


fromCharCode

Returns a string created by using the specified sequence of Unicode values.



Method of  

String  

Static

Implemented in  

JavaScript 1.2, NES 3.0

JavaScript 1.3: uses a Unicode value rather than an ISO-Latin-1 value.  

ECMA version  

ECMA-262  


Syntax
fromCharCode(num1, ..., numN)


Parameters



num1, ..., numN

 

A sequence of numbers that are Unicode values.  


Description
This method returns a string and not a 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.


Backward Compatibility

JavaScript 1.2. The fromCharCode method returns a string created by using the specified sequence of ISO-Latin-1 codeset values.


Examples
The following example returns the string "ABC".

String.fromCharCode(65,66,67)


indexOf

Returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex, or -1 if the value is not found.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  

ECMA version  

ECMA-262  


Syntax
indexOf(searchValue[, fromIndex])


Parameters



searchValue

 

A string representing the value to search for.  

fromIndex

 

The location within the calling string to start the search from. It can be any integer between 0 and the length of the string. The default value is 0.  


Description
Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character of a string called stringName is stringName.length - 1.

"Blue Whale".indexOf("Blue")    // returns 0
"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

The indexOf method is case sensitive. For example, the following expression returns -1:

"Blue Whale".indexOf("blue")


Examples
Example 1. The following example uses 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"))

Example 2. The following example defines two string variables. The variables contain the same string except that the second string contains uppercase letters. The first 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"
myCapString="Brie, Pepper Jack, Cheddar"
document.writeln('myString.indexOf("cheddar") is ' +
   myString.indexOf("cheddar"))
document.writeln('<P>myCapString.indexOf("cheddar") is ' +
   myCapString.indexOf("cheddar"))

Example 3. The following example sets 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);
}


See also
String.charAt, String.lastIndexOf, String.split


italics

Causes a string to be italic, as if it were in an <I> tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
italics()


Parameters
None


Description
Use the 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.


Examples
The following example uses string methods to change the formatting of a string:

var worldString="Hello, world"

document.write(worldString.blink())
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())

The previous example produces the same output as the following HTML:

<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>


See also
String.blink, String.bold, String.strike


lastIndexOf

Returns the index within the calling String object of the last occurrence of the specified value, or -1 if not found. The calling string is searched backward, starting at fromIndex.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  

ECMA version  

ECMA-262  


Syntax
lastIndexOf(searchValue[, fromIndex])


Parameters



searchValue

 

A string representing the value to search for.  

fromIndex

 

The location within the calling string to start the search from. It can be any integer between 0 and the length of the string. The default value is the length of the string.  


Description
Characters in a string are indexed from left to right. The index of the first character is 0, and the index of the last character is stringName.length - 1.

"canal".lastIndexOf("a")   // returns 3
"canal".lastIndexOf("a",2) // returns 1
"canal".lastIndexOf("a",0) // returns -1
"canal".lastIndexOf("x")   // returns -1

The lastIndexOf method is case sensitive. For example, the following expression returns -1:

"Blue Whale, Killer Whale".lastIndexOf("blue")


Examples
The following example uses 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"))


See also
String.charAt, String.indexOf, String.split


length

The length of the string.



Property of  

String  

Read-only

Implemented in  

JavaScript 1.0, NES 2.0  

ECMA version  

ECMA-262  


Description
For a null string, length is 0.


Examples
The following example displays 8 in an Alert dialog box:

var x="Netscape"
alert("The string length is " + x.length)


link

Creates an HTML hypertext link that requests another URL.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
link(hrefAttribute)


Parameters



hrefAttribute

 

Any string that specifies the HREF attribute of the A tag; it should be a valid URL (relative or absolute).  


Description
Use the 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.


Examples
The following example displays the word "Netscape" as a hypertext link that returns the user to the Netscape home page:

var hotText="Netscape"
var URL="http://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>


match

Used to match a regular expression against a string.



Method of  

String  

Implemented in  

JavaScript 1.2  

ECMA version  

ECMA-262 Edition 3  


Syntax
match(regexp)


Parameters



regexp

 

Name of the regular expression. It can be a variable name or a literal.  


Description
If the regular expression does not include the g flag, returns the same result that RegExp.exec would return on the regular expression and string. If the regular expression includes the g flag, returns an array of all the matches of the regular expression in the string.

Note If you execute a match simply to find true or false, use String.search or the regular expression test method.


Examples
Example 1. In the following example, 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>
str = "For more information, see Chapter 3.4.5.1";
re = /(chapter \d+(\.\d)*)/i;
found = str.match(re);
document.write(found);
</SCRIPT>

This returns the array containing Chapter 3.4.5.1,Chapter 3.4.5.1,.1

'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>
str = "abcDdcba";
newArray = str.match(/d/gi);
document.write(newArray);
</SCRIPT>

The returned array contains D, d.


prototype

Represents the prototype for this class. You can use the prototype to add properties or methods to all instances of a class. For information on prototypes, see Function.prototype.



Property of  

String  

Implemented in  

JavaScript 1.1, NES 3.0  

ECMA version  

ECMA-262  


replace

Finds a match between a regular expression and a string, and replaces the matched substring with a new substring.



Method of  

String  

Implemented in  

JavaScript 1.2

JavaScript 1.3: added the ability to specify a function as the second parameter.  

ECMA version  

ECMA-262 Edition 3  


Syntax
replace(regexp, newSubStr)
replace(regexp, function)

Versions prior to JavaScript 1.3:

replace(regexp, newSubStr)


Parameters



regexp

 

The name of the regular expression. It can be a variable name or a literal.  

newSubStr

 

The string to put in place of the string found with regexp.  

function

 

A function to be invoked after the match has been performed.  


Description
This method does not change the String object it is called on. It simply returns a new string.

If you want to execute a global search and replace, include the g flag in the regular expression.

Specifying a string as a parameter. The replacement string can include the following special replacement patterns:




$$  

Inserts a '$'.  

$&  

Inserts the matched substring..  

$`  

Inserts the portion of the string that precedes the matched substring.  

 

Inserts the portion of the string that follows the matched substring.  

$n
or
$nn
 

Where n or nn are decimal digits, inserts the nth parenthesized submatch string.  

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. The following n parameters can be used for parenthetical matches, remembered submatch strings, where n is the number of submatch strings in the regular expression. Finally, the last two parameters are the offset within the string where the match occurred and the string itself. For example, the following replace method returns XX.zzzz - XX , zzzz.

"XXzzzz".replace(/(X*)(z*)/,
                   function (str, p1, p2, offset, s) {
                      return str + " - " + p1 + " , " + p2;
                   }
                )


Backward Compatibility

JavaScript 1.2. You cannot specify a function to be invoked after the match has been performed.


Examples
Example 1. In the following example, the regular expression includes the global and ignore case flags which permits replace to replace each occurrence of 'apples' in the string with 'oranges.'

<SCRIPT>
re = /apples/gi;
str = "Apples are round, and apples are juicy.";
newstr=str.replace(re, "oranges");
document.write(newstr)
</SCRIPT>

This prints "oranges are round, and oranges are juicy."

Example 2. In the following example, the regular expression is defined in replace and includes the ignore case flag.

<SCRIPT>
str = "Twas the night before Xmas...";
newstr=str.replace(/xmas/i, "Christmas");
document.write(newstr)
</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 $1 and $2 replacement patterns.

<SCRIPT LANGUAGE="JavaScript1.2">
re = /(\w+)\s(\w+)/;
str = "John Smith";
newstr = str.replace(re, "$2, $1");
document.write(newstr)
</SCRIPT>

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 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,
         function (str,p1,offset,s) {
            return ((p1-32) * 5/9) + "C";
         }
      )
}


search

Executes the search for a match between a regular expression and this String object.



Method of  

String  

Implemented in  

JavaScript 1.2  

ECMA version  

ECMA-262 Edition 3  


Syntax
search(regexp)


Parameters



regexp

 

Name of the regular expression. It can be a variable name or a literal.  


Description
If successful, 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).


Example
The following example prints a message which depends on the success of the test.

function testinput(re, str){
   if (str.search(re) != -1)
      midstring = " contains ";
   else
      midstring = " does not contain ";
   document.write (str + midstring + re.source);
}


slice

Extracts a section of a string and returns a new string.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  

ECMA version  

ECMA-262 Edition 3  


Syntax
slice(beginslice[, endSlice])


Parameters



beginSlice

 

The zero-based index at which to begin extraction.  

endSlice

 

The zero-based index at which to end extraction. If omitted, slice extracts to the end of the string.  


Description
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.


Example
The following example uses slice to create a new string.

<SCRIPT>
str1="The morning is upon us. "
str2=str1.slice(3,-5)
document.write(str2)
</SCRIPT>

This writes:

morning is upon


small

Causes a string to be displayed in a small font, as if it were in a <SMALL> tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
small()


Parameters
None


Description
Use the 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.


Examples
The following example uses string methods to change the size of a string:

var worldString="Hello, world"

document.write(worldString.small())
document.write("<P>" + worldString.big())
document.write("<P>" + worldString.fontsize(7))

The previous example produces the same output as the following HTML:

<SMALL>Hello, world</SMALL>
<P><BIG>Hello, world</BIG>
<P><FONTSIZE=7>Hello, world</FONTSIZE>


See also
String.big, String.fontsize


split

Splits a String object into an array of strings by separating the string into substrings.



Method of  

String  

Implemented in  

JavaScript 1.1, NES 2.0  

ECMA version  

ECMA-262 (if separator is a string)
ECMA-262 Edition 3 (if separator is a regular expression)
 


Syntax
split([separator][, limit])


Parameters



separator

 

Specifies the character to use for separating the string. The separator is treated as a string or a regular expression. If separator is omitted, the array returned contains one element consisting of the entire string.  

limit

 

Integer specifying a limit on the number of splits to be found.  


Description
The 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 or later, split has the following additions:

  • It can take a regular expression argument, as well as a fixed string, by which to split the object string. If separator is a regular expression, any included parenthesis cause submatches to be included in the returned array.

  • It can take a limit count so that the resulting array does not include trailing empty elements.

  • If you specify 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.

Examples
Example 1. The following example defines a function that splits a string into an array of strings using the specified separator. After splitting the string, the function displays messages indicating the original string (before the split), the separator used, the number of elements in the array, and the individual array elements.

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)
splitString(tempestString)
splitString(monthString,comma)

This example produces the following output:

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"
The separator is: ","
The array has 12 elements: Jan / Feb / Mar / Apr / May / Jun / Jul / Aug / Sep / Oct / Nov / Dec /

Example 2. Consider the following script:

<SCRIPT LANGUAGE="JavaScript1.2">
str="She sells seashells \nby the\n seashore"
document.write(str + "<BR>")
a=str.split(" ")
document.write(a)
</SCRIPT>

Using 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>
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>

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
Harry Trump,Fred Barney,Helen Rigby,Bill Abel,Chris Hand

Example 4. In the following example, split looks for 0 or more spaces in a string and returns the first 3 splits that it finds.

<SCRIPT LANGUAGE="JavaScript1.2">
myVar = " Hello World. How are you doing? ";
splits = myVar.split(" ", 3);
document.write(splits)
</SCRIPT>

This script displays the following:

["Hello", "World.", "How"]


See also
String.charAt, String.indexOf, String.lastIndexOf


strike

Causes a string to be displayed as struck-out text, as if it were in a <STRIKE> tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
strike()


Parameters
None


Description
Use the 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.


Examples
The following example uses string methods to change the formatting of a string:

var worldString="Hello, world"

document.write(worldString.blink())
document.write("<P>" + worldString.bold())
document.write("<P>" + worldString.italics())
document.write("<P>" + worldString.strike())

The previous example produces the same output as the following HTML:

<BLINK>Hello, world</BLINK>
<P><B>Hello, world</B>
<P><I>Hello, world</I>
<P><STRIKE>Hello, world</STRIKE>


See also
String.blink, String.bold, String.italics


sub

Causes a string to be displayed as a subscript, as if it were in a <SUB> tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
sub()


Parameters
None


Description
Use the 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.


Examples
The following example uses the sub and sup methods to format a string:

var superText="superscript"
var subText="subscript"

document.write("This is what a " + superText.sup() + " looks like.")
document.write("<P>This is what a " + subText.sub() + " looks like.")

The previous example produces the same output as the following HTML:

This is what a <SUP>superscript</SUP> looks like.
<P>This is what a <SUB>subscript</SUB> looks like.


See also
String.sup


substr

Returns the characters in a string beginning at the specified location through the specified number of characters.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
substr(start[, length])


Parameters



start

 

Location at which to begin extracting characters.  

length

 

The number of characters to extract.  


Description
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.


Example
Consider the following script:

<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):


See also
substring


substring

Returns a subset of a String object.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  

ECMA version  

ECMA-262  


Syntax
substring(indexA, indexB)


Parameters



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.  


Description
substring extracts characters from indexA up to but not including indexB. In particular:

  • If indexA is less than 0, indexA is treated as if it were 0.

  • If indexB is greater than stringName.length, indexB is treated as if it were stringName.length.

  • If indexA equals indexB, substring returns an empty string.

  • If indexB is omitted, indexA extracts characters to the end of the string.
In JavaScript 1.2, using LANGUAGE="JavaScript1.2" in the SCRIPT tag,
  • If indexA is greater than indexB, JavaScript produces a runtime error (out of memory).
In JavaScript 1.2, without LANGUAGE="JavaScript1.2" in the SCRIPT tag,
  • If indexA is greater than indexB, JavaScript returns a substring beginning with indexB and ending with indexA - 1.

Examples
Example 1. The following example uses substring to display characters from the string "Netscape":

var anyString="Netscape"

// Displays "Net"
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))

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 "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">
str="Netscape"
document.write(str.substring(0,3);
document.write(str.substring(3,0);
</SCRIPT>

Without LANGUAGE="JavaScript1.2", the above script prints the following:

Net Net

In the second write, the index numbers are swapped.


See also
substr


sup

Causes a string to be displayed as a superscript, as if it were in a <SUP> tag.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  


Syntax
sup()


Parameters
None


Description
Use the 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.


Examples
The following example uses the sub and sup methods to format a string:

var superText="superscript"
var subText="subscript"

document.write("This is what a " + superText.sup() + " looks like.")
document.write("<P>This is what a " + subText.sub() + " looks like.")

The previous example produces the same output as the following HTML:

This is what a <SUP>superscript</SUP> looks like.
<P>This is what a <SUB>subscript</SUB> looks like.


See also
String.sub


toLowerCase

Returns the calling string value converted to lowercase.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  

ECMA version  

ECMA-262  


Syntax
toLowerCase()


Parameters
None


Description
The toLowerCase method returns the value of the string converted to lowercase. toLowerCase does not affect the value of the string itself.


Examples
The following example displays the lowercase string "alphabet":

var upperText="ALPHABET"
document.write(upperText.toLowerCase())


See also
String.toUpperCase


toSource

Returns a string representing the source code of the object.



Method of  

String  

Implemented in  

JavaScript 1.3  


Syntax
toSource()


Parameters
None


Description
The toSource method returns the following values:

  • For the built-in String object, toSource returns the following string indicating that the source code is not available:

       function String() {
          [native code]
       }

  • For instances of String or string literals, toSource returns a string representing the source code.
This method is usually called internally by JavaScript and not explicitly in code.


toString

Returns a string representing the specified object.



Method of  

String  

Implemented in  

JavaScript 1.1, NES 2.0  

ECMA version  

ECMA-262  


Syntax
toString()


Parameters
None.


Description
The 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.


Examples
The following example displays the string value of a String object:

x = new String("Hello world");
alert(x.toString())      // Displays "Hello world"


See also
Object.toString


toUpperCase

Returns the calling string value converted to uppercase.



Method of  

String  

Implemented in  

JavaScript 1.0, NES 2.0  

ECMA version  

ECMA-262  


Syntax
toUpperCase()


Parameters
None


Description
The toUpperCase method returns the value of the string converted to uppercase. toUpperCase does not affect the value of the string itself.


Examples
The following example displays the string "ALPHABET":

var lowerText="alphabet"
document.write(lowerText.toUpperCase())


See also
String.toLowerCase


valueOf

Returns the primitive value of a String object.



Method of  

String  

Implemented in  

JavaScript 1.1  

ECMA version  

ECMA-262  


Syntax
valueOf()


Parameters
None


Description
The 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.


Examples
x = new String("Hello world");
alert(x.valueOf())          // Displays "Hello world"


See also
String.toString, Object.valueOf


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Last Updated September 28, 2000

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