The String object lets you work with a
series of characters; it wraps Javascript's string primitive data type with a
number of helper methods.
As JavaScript
automatically converts between string primitives and String objects, you can
call any of the helper methods of the String object on a string primitive.
Syntax
Use the following syntax to create a String object:
var val = new
String(string);
The string parameter is a
series of characters that has been properly encoded.
String Properties
Here is a list of the properties of String object and their
description.
Property
|
Description
|
constructor
|
Returns
a reference to
the String function
that created the
|
object.
|
|
Length
|
Returns the length of the string.
|
prototype
|
The
prototype property allows
you to add
properties and
|
methods to an object.
|
|
In the following sections, we will have a few
examples to demonstrate the usage of String properties.
constructor
A constructor returns a reference to the
string function that created the instance's prototype.
Syntax
Its syntax is as follows:
string.constructor
Return Value
Returns the function that created this object's instance.
Example
Try the following example.
<html>
<head>
<title>JavaScript
String constructor property</title>
</head>
<body>
<script
type="text/javascript">
var str =
new String( "This is string" ); document.write("str.constructor
is:" + str.constructor);
</script>
</body>
</html>
Output
str.constructor
is:function String() { [native code] }
Length
This property returns the number of characters in a string.
Syntax
Use the following syntax to find the length of a string:
string.length
Return Value
Returns the number of characters in the string.
Example
Try the following example.
<html>
<head>
<title>JavaScript
String length Property</title>
</head>
<body>
<script
type="text/javascript">
var str =
new String( "This is string" ); document.write("str.length
is:" + str.length);
</script>
</body>
</html>
Output
str.length is:14
Prototype
The prototype property allows you to add
properties and methods to any object (Number, Boolean, String, Date, etc.).
Note: Prototype is a global
property which is available with almost all the objects.
Syntax
Its syntax is as follows:
object.prototype.name
= value
Example
Try the following example.
<html>
<head>
<title>User-defined
objects</title>
<script
type="text/javascript">
function
book(title, author){
this.title =
title;
this.author = author;
}
</script>
</head>
<body>
<script
type="text/javascript">
var
myBook = new book("Perl", "Mohtashim");
book.prototype.price = null; myBook.price = 100;
document.write("Book
title is : " + myBook.title + "<br>");
document.write("Book
author is : " + myBook.author + "<br>");
document.write("Book
price is : " + myBook.price + "<br>");
</script>
</body>
</html>
Output
Book title is :
Perl
Book author is :
Mohtashim
Book price is :
100
String Methods
Here is a list of the methods available in
String object along with their description.
Method
|
Description
|
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.
|
||
indexOf()
|
Returns the index within the calling String
object of the
|
|
first occurrence of the specified value, or
-1 if not found.
|
||
lastIndexOf()
|
Returns the index within the calling String
object of the
|
|
last occurrence of the specified value, or
-1 if not found.
|
||
localeCompare()
|
Returns a number indicating whether a
reference string
|
|
comes before or after or is the same as the
given string
|
||
in sorted order.
|
||
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.
|
|
split()
|
Splits
a String object
into an array
of strings by
|
|
separating the string into substrings.
|
||
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.
|
||
toLocaleLowerCase()
|
The characters within a string are converted
to lower
|
|
case while respecting the current locale.
|
||
toLocaleUpperCase()
|
The characters within a string are converted
to upper
|
|
case while respecting the current locale.
|
||
toLowerCase()
|
Returns the calling string value converted
to lower case.
|
|
toString()
|
Returns a string representing the specified
object.
|
|
toUpperCase()
|
Returns the calling string value converted
to uppercase.
|
|
valueOf()
|
Returns the primitive value of the specified
object.
|
|
In the following
sections, we will have a few examples to demonstrate the usage of String
methods.
charAt()
charAt() is a method that returns the character from the specified
index.
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.
Syntax
Use the following syntax to find the character at a particular index.
string.charAt(index)
Argument Details
index: An integer between 0 and 1 less than the
length of the string.
Return Value
Returns the character from the specified index.
Example
Try the following example.
<html>
<head>
<title>JavaScript
String charAt() Method</title>
</head>
<body>
<script
type="text/javascript">
var str =
new String( "This is string" ); document.writeln("str.charAt(0)
is:" + str.charAt(0)); document.writeln("<br />str.charAt(1)
is:" + str.charAt(1)); document.writeln("<br />str.charAt(2)
is:" + str.charAt(2));
document.writeln("<br />str.charAt(3) is:" +
str.charAt(3)); document.writeln("<br />str.charAt(4) is:" +
str.charAt(4)); document.writeln("<br />str.charAt(5) is:" +
str.charAt(5));
</script>
</body>
</html>
Output
str.charAt(0) is:T
str.charAt(1) is:h
str.charAt(2) is:i
str.charAt(3) is:s
str.charAt(4) is:
str.charAt(5) is:i
charCodeAt ()
This method returns a
number indicating the Unicode value of the character at the given index.
Unicode code points
range from 0 to 1,114,111. The first 128 Unicode code points are a direct match
of the ASCII character encoding. charCodeAt()
always returns a value that is less than 65,536.
Syntax
Use the following syntax to find the character code at a particular
index.
string.charCodeAt(index)
Argument Details
index: An integer between 0 and 1 less than the length of the string; if unspecified, defaults to 0.
Return Value
Returns a number
indicating the Unicode value of the character at the given index. It returns
NaN if the given index is not between 0 and 1 less than the length of the
string.
Example
Try the following example.
<html>
<head>
<title>JavaScript
String charCodeAt() Method</title>
</head>
<body>
<script
type="text/javascript">
var str =
new String( "This is string" );
document.write("str.charCodeAt(0) is:" + str.charCodeAt(0));
document.write("<br />str.charCodeAt(1) is:" +
str.charCodeAt(1)); document.write("<br />str.charCodeAt(2)
is:" + str.charCodeAt(2)); document.write("<br
/>str.charCodeAt(3) is:" + str.charCodeAt(3));
document.write("<br />str.charCodeAt(4) is:" +
str.charCodeAt(4)); document.write("<br />str.charCodeAt(5)
is:" + str.charCodeAt(5));
</script>
</body>
</html>
Output
str.charCodeAt(0)
is:84
str.charCodeAt(1)
is:104
str.charCodeAt(2)
is:105
str.charCodeAt(3)
is:115
str.charCodeAt(4)
is:32
str.charCodeAt(5)
is:105
contact ()
This method adds two or more strings and returns a new single string.
Syntax
Its syntax is as follows:
string.concat(string2,
string3[, ..., stringN]);
Argument Details
string2...stringN: These are the strings to be concatenated.
Return Value
Returns a single concatenated string.
Example
Try the following example.
<html>
<head>
<title>JavaScript
String concat() Method</title>
</head>
<body>
<script
type="text/javascript">
var str1
= new String( "This is string one" ); var str2 = new String(
"This is string two" ); var str3 = str1.concat( str2 );
document.write("Concatenated
String :" + str3);
</script>
</body>
</html>
Output
Concatenated
String :This is string one This is string two
indexOf ()
This method 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.
Syntax
Use the following syntax to use the indexOf() method.
string.indexOf(searchValue[,
fromIndex])
Argument Details
·
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.
Return Value
Returns the index of the found occurrence, otherwise -1 if not found.
Example
Try the following example.
<html>
<head>
<title>JavaScript
String indexOf() Method</title>
</head>
<body>
<script
type="text/javascript">
var str1
= new String( "This is string one" ); var index = str1.indexOf(
"string" ); document.write("indexOf found String :" + index
);
document.write("<br
/>");
var index
= str1.indexOf( "one" ); document.write("indexOf found String
:" + index );
</script>
</body>
</html>
Output
indexOf found
String :8
indexOf found
String :15
lastIndexOf ()
This method returns the
index within the calling String object of the last occurrence of the specified
value, starting the search at fromIndex
or -1 if the value is not found.
Syntax
Its syntax is as follows:
string.lastIndexOf(searchValue[,
fromIndex])
Argument Details
·
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.
Return Value
Returns the index of the last found occurrence, otherwise -1 if not
found.
Example
Try the following example.
<html>
<head>
<title>JavaScript
String lastIndexOf() Method</title>
</head>
<body>
<script
type="text/javascript">
var str1
= new String( "This is string one and again string" ); var index =
str1.lastIndexOf( "string" ); document.write("lastIndexOf found
String :" + index );
document.write("<br
/>");
var index
= str1.lastIndexOf( "one" ); document.write("lastIndexOf found
String :" + index );
</script>
</body>
</html>
Output
lastIndexOf found
String :29
lastIndexOf found
String :15
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