From http://www.w3schools.com (Copyright Refsnes Data)

JavaScript String Object

The String object is used to manipulate a stored piece of text.

Examples

Return the length of a string
How to use the length property to find the length of a string.

Style strings
How to style strings.

The indexOf() method
How to use the indexOf() method to return the position of the first occurrence of a specified string value in a string.

The match() method
How to use the match() method to search for a specified string value within a string and return the string value if found

Replace characters in a string - replace()
How to use the replace() method to replace some characters with some other characters in a string.

For a complete reference of all the properties and methods that can be used with the String object, go to our complete String object reference.

The reference contains a brief description and examples of use for each property and method!

The String object is used to manipulate a stored piece of text.

Examples of use:

The following example uses the length property of the String object to find the length of a string:

var txt="Hello world!";
document.write(txt.length);

The code above will result in the following output:

The following example uses the toUpperCase() method of the String object to convert a string to uppercase letters:

var txt="Hello world!";
document.write(txt.toUpperCase());

The code above will result in the following output:

HELLO WORLD!