String

Summary

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

Syntax

// Declaring a string literal.
var newString = "stringLiteral";

// Or, declaring a String object - discouraged, long, verbose and pretty useless.
var newString = new String([" stringLiteral "]);

newString: Required. The variable name to which the String object is assigned.
stringLiteral: Optional. Any group of Unicode characters.

Examples

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 (JScript).

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 shows that the data type of a string literal is not the same as that of a String object.

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

document.write(typeof strLit);
document.write("<br/>");
document.write(typeof strObj);
// Output:
// string
// object

When you call a method on a string literal, it is temporarily converted to a string wrapper object. The string literal is treated as though the new operator were used to create it.

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

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

var result1 = strLit.toUpperCase();

var result2 = (new String(strLit)).toUpperCase();

document.write(result1);
document.write("<br/>");
document.write(result2);
// Output:
// THIS IS A STRING LITERAL.
// THIS IS A STRING LITERAL.

In modern browsers (2011 onwards), you can access an individual character of a string as a read-only array-indexed property. 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

Properties

The following table lists the properties of the String object.

Property	Description
constructor	Specifies the function that creates an object.
length	Returns the length of a String object.
prototype	Returns a reference to the prototype for a class of objects.

Functions

The following table lists the functions of the String object.

Function	Description
fromCharCode	Returns a string from a number of Unicode character values.

Methods

The following table lists the methods of the String object.

Method	Description
HTML Tag Methods	Places various HTML tags around text.
charAt	Returns the character at the specified index.
charCodeAt	Returns the Unicode encoding of the specified character.
concat	Returns a string that contains the concatenation of two supplied strings.
indexOf	Returns the character position where the first occurrence of a substring occurs within a string.
lastIndexOf	Returns the last occurrence of a substring within a string.
localeCompare	Returns a value that indicates whether two strings are equivalent in the current locale.
match	Searches a string by using a supplied Regular Expression object and returns the results as an array.
replace	Uses a regular expression to replace text in a string and returns the result.
search	Returns the position of the first substring match in a regular expression search.
slice	Returns a section of a string.
split	Returns the array of strings that results when a string is separated into substrings.
substr	Returns a substring beginning at a specified location and having a specified length.
substring	Returns the substring at a specified location within a String object.
toLocaleLowerCase	Returns a string in which all alphabetic characters are converted to lowercase, taking into account the host environment’s current locale.
toLocaleUpperCase	Returns a string in which all alphabetic characters are converted to uppercase, taking into account the host environment’s current locale.
toLowerCase	Returns a string in which all alphabetic characters are converted to lowercase.
toString	Returns the string.
toUpperCase	Returns a string in which all alphabetic characters are converted to uppercase.
trim	Returns a string with leading and trailing white space and line terminator characters removed.
valueOf	Returns the string.

Attributions

Microsoft Developer Network: Article