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String Object (JavaScript)

Allows manipulation and formatting of text strings and determination and location of substrings within strings.

newString = new String(["stringLiteral"])

newString

Required. The variable name to which the String object is assigned.

stringLiteral

Optional. Any group of Unicode characters.

JavaScript provides escape sequences that you can include in strings to create characters that you cannot type directly. For example, \t specifies a tab character. For more information, see Special Characters (JavaScript).

Data Types

A string literal is zero or more characters enclosed in single or double quotation marks. A string literal has a primary (primitive) data type of string. A String object is created by using the new Operator, and has a data type of object.

The following example defines a string literal and a string object and determines their data types.

// Define a string literal and a string object.
var strLit = "This is a string literal.";
var strObj = new String("This is a string object.");

// Display the types of the string literal and object.
alert(typeof strLit);
// Output: string

alert(typeof strObj);
// Output: object

Methods for String Literals

When JavaScript accesses a method of a primitive string, the string is temporarily converted to a string wrapper object. JavaScript accesses the method from the wrapper object. The primitive string is treated as if the new operator were used to create it.

The following example applies the toUpperCase method to a primitive string.

var strLit = "This is a string literal.";

// Return a string converted to uppercase.
// The strLit primitive string is converted to a temporary
// wrapper object that accesses the toUpperCase method.
var result = strLit.toUpperCase();

// This statement is equivalent to the above statement.
var result = (new String(strLit)).toUpperCase();
// Output: THIS IS A STRING LITERAL.

Accessing an Individual Character

You can access an individual character of a string as a read-only array-indexed property. This feature was introduced in Internet Explorer 9 standards mode. The following example accesses individual string characters.

var str = "abcd";
var result = str[2];
document.write (result);
// Output: c

var result = "the"[0];
document.write(result);
// Output: t

Adding Properties Dynamically

A String object declared with the new operator can have its own set of dynamically created properties. In the following example, the test property defined for the gamma object is not defined for delta.

var gamma = new String("This is a string");
var delta = new String("This is also a string");

gamma.test = 10;

The String Object was introduced in Internet Explorer before Internet Explorer 6. Some members in the following lists were introduced in later versions.

The following table lists the properties of the String object.

Property

Description

constructor Property

Specifies the function that creates an object.

length Property (String)

Returns the length of a String object.

prototype Property

Returns a reference to the prototype for a class of objects.

The following table lists the functions of the String object.

Function

Description

String.fromCharCode Function

Returns a string from a number of Unicode character values.

The following table lists the methods of the String object.

Method

Description

anchor Method

Places an HTML anchor that has a NAME attribute around text.

big Method

Places HTML <BIG> tags around text.

blink Method

Places HTML <BLINK> tags around text.

bold Method

Places HTML <B> tags around text.

charAt Method

Returns the character at the specified index.

charCodeAt Method

Returns the Unicode encoding of the specified character.

concat Method (String)

Returns a string that contains the concatenation of two supplied strings.

fixed Method

Places HTML <TT> tags around text.

fontcolor Method

Places HTML <FONT> tags with a COLOR attribute around text.

fontsize Method

Places HTML <FONT> tags with a SIZE attribute around text.

hasOwnProperty Method

Returns a Boolean value that indicates whether an object has a property with the specified name.

indexOf Method (String)

Returns the character position where the first occurrence of a substring occurs within a string.

isPrototypeOf Method

Returns a Boolean value that indicates whether an object exists in another object's prototype chain.

italics Method

Places HTML <I> tags around text.

lastIndexOf Method (String)

Returns the last occurrence of a substring within a string.

link Method

Places an HTML anchor that has an HREF attribute around text.

localeCompare Method

Returns a value that indicates whether two strings are equivalent in the current locale.

match Method

Searches a string by using a supplied Regular Expression object and returns the results as an array.

propertyIsEnumerable Method

Returns a Boolean value that indicates whether a specified property is part of an object and whether it is enumerable.

replace Method

Uses a regular expression to replace text in a string and returns the result.

search Method

Returns the position of the first substring match in a regular expression search.

slice Method (String)

Returns a section of a string.

small Method

Places HTML <SMALL> tags around text.

split Method

Returns the array of strings that results when a string is separated into substrings.

strike Method

Places HTML <STRIKE> tags around text.

sub Method

Places HTML <SUB> tags around text.

substr Method

Returns a substring beginning at a specified location and having a specified length.

substring Method

Returns the substring at a specified location within a String object.

sup Method

Places HTML <SUP> tags around text.

toLocaleLowerCase Method

Returns a string in which all alphabetic characters are converted to lowercase, taking into account the host environment's current locale.

toLocaleString Method

Returns an object converted to a string, using the current locale.

toLocaleUpperCase Method

Returns a string in which all alphabetic characters are converted to uppercase, taking into account the host environment's current locale.

toLowerCase Method

Returns a string in which all alphabetic characters are converted to lowercase.

toString Method

Returns a string representation of an object.

toUpperCase Method

Returns a string in which all alphabetic characters are converted to uppercase.

trim Method

Returns a string with leading and trailing white space and line terminator characters removed.

valueOf Method

Returns the primitive value of the specified object.

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