Explain how to Manipulate the Strings in Java Script

String refers to series of characters (alphabets, special characters, numbers and combination of them) enclosed in double quotations.

Most of the data in java script is text strings, sum of the most useful text manipulations involve ‘regular expression’ string. Calls allows you to store text and also let’s you to do process on it.

There are two ways to store text strings.

Syntax: var name = “ string”

                        (or)

              var name  = new String (“ string name”);

String manipulations:

1. Joining strings together.

2. Spliting the string.

3.Searching for a letter (or) word in the given string.

‘String class’ contains number of methods:

Syntax:   Objectname . Method( );

Methods:

1. charAt (index):

This function returns a character whose index value is supplied as an argument to the function.

Eg: var name = “SAI”;

document.write (name. chartAt(2));

o/p: ‘I’

NOTE: If there is no character available in the specified location then an empty string is returned.

2.concat (“String”[,”string”[,…….”stirng”]]);

It combines two strings. Java script has two ways that it can join strings together.

1) The simplest way is to use the ‘+’ operator

Syntax: var name = prompt (“ enter you name”,” “);

              var age = prompt (“enter your age”,” “);

              var res = name + age;

2) Using ‘concant’ key word.

Syntax: Var masg = “ Thank you”;

              document. write (msg.concat (name));

3.indexOf (“search”L, offset]);

The string is searched for the string (or) quoted character in the first parameter.

If search is successful it returns the first occurrence of a specified string.

If the search is unsuccessful the operation returns minus value.

By default the index of function starts at index ‘O’.

Eg: var name = “nadeem”;

       document. write (name. indexOf (“e”));

       o/p:3

4. lastIndexOf (“search”[,offset]): 

This function also does exactly the same thing as index of, but works its way backwards along the string.It returns position of last occurrence of a specified position in a string.

Eg: var name = “nadeem”;

      document. write (name.lastIndexOf (“e”));

      o/p:- 4

5.Length:

Value which holds the no.of characters in a string. This is not a function so do not have to place paranthesis when using it.

Eg. var name = “nadeem”l

       var len = name.length;

       o/p:- 6.

6. Split (separator [limit]): 

It takes an argument of character and splits the source string into sub string w.r.to the character supplied.

Eg:- var name = “nadeem”;

        document.write (name.split(“e”));

        o/p:- nad, m

split function breaks the string apart whenever it encounters a character passed in as the first parameter.These pieces of strings are stored in an array.

Split has an optional second parameter which is an integer value indicating how many of the pieces are to be stored in an array.

.7.substr(index [,length]): 

The function returns a substring which starts at the character indicated by index parameter.

 It takes two arguments index, end/length  respectively. here ‘index’ argument specifies the initiating character, the length argument specifies the length of the character to be displayed.

Eg:- var name = “nadeem”;

        document. write (name. substr(1,2));

        o/p:- ad.

The substring continuous either to the end of the string (or) the no.of characters indicated by the length parameter. If the index is greater than the length of the string then nothing is returned.

8.toLowerCase: 

Converts all characters in the strings to lower case. If the string contains few non-characters then they remain unchanged.

9.toUpperCase:

Converts all characters in the string to upper case.

Eg. var name = “nadeem”;

       document.write (name.toUpperCase());

       o/p:- NADEEM.

10.subString (index1[index 2]:-

This function returns a set of characters which starts from index 1 and continuous upto, but does not include the character at index 2.

It takes two arguments index & end respectively here index argument specifies the initiating character and the end specifies the last character to be displayed.

Eg:- var name = “NADEEM”,

        document.write (name. subString (1, 4));

        o/p:- ade

The following rules are applied:

1) If index 1 is less than ‘o’ it will be treated as ‘0’.

2) If index 2 is greater than the length of the string it will be treated as the length of the string

3) If the two index values are equal on empty string is returned.

4) If index 2 is missing all characters upto the end of the string are taken.

5) If index 1 is greater than index 2 the run time error occurs.