String Object Methods in JavaScript

Introduction
 
In this article we will learn various string object methods in JavaScript. As we know JavaScript is an object oriented language and everything is treated as an object in JavaScript. String is also one type of object in JavaScript.

Method

Description

indexOf()

Returns the position of the first found occurrence of a specified value in a string

charAt()

Returns the character at the specified index

replace()

Searches for a match between a substring (or regular expression) and a string, and replaces the matched substring with a new substring

substring()

Extracts the characters from a string, between two specified indices

toLowerCase()

Converts a string to lowercase letters

toUpperCase()

Converts a string to uppercase letters


Let us understand one by one with an example.
 
 
Index of Function
 
The indexOf function returns the position of the first occurrence of a specified value in a string. In the following example we are trying to find the index of "s" in the "a" string.
 
 
  1. <!DOCTYPE html>  
  2. <html xmlns="http://www.w3.org/1999/xhtml">  
  3. <head runat="server">  
  4.        
  5. </head>  
  6. <body>  
  7.     <form id="form1" runat="server">  
  8.         <script>  
  9.             var a = "RamaSagar";  
  10.             alert(a.indexOf('S'));  
  11.         </script>  
  12.     </form>  
  13. </body>  
  14. </html>  
 
Output
 
 
 
 charAt() Function
 
This function returns the character at a specific position. It takes one integer argument specifying an index of the string. Here is a code snippet to understand the charAt() function.
 
 
  1. <!DOCTYPE html>  
  2. <html xmlns="http://www.w3.org/1999/xhtml">  
  3. <head runat="server">  
  4.        
  5. </head>  
  6. <body>  
  7.     <form id="form1" runat="server">  
  8.         <script>  
  9.             var a = "RamaSagar";  
  10.             alert(a.charAt(2));  
  11.         </script>  
  12.     </form>  
  13. </body>  
  14. </html>  
 Output
 
 
 
 
Replace() Function
 
 This function replaces a part of a string with some other string. It uses pattern matching to replace the part of the string. In this example string we are replacing “Rama” by the string “Replaced”. 
 
 
  1. <!DOCTYPE html>  
  2. <html xmlns="http://www.w3.org/1999/xhtml">  
  3. <head runat="server">  
  4.        
  5. </head>  
  6. <body>  
  7.     <form id="form1" runat="server">  
  8.         <script>  
  9.             var a = "RamaSagar";  
  10.             alert(a.replace("Rama","Replaced"));  
  11.         </script>  
  12.     </form>  
  13. </body>  
  14. </body>  
  15. </html>  
 
Output
 
 
 
 
substring() Function 
 
The substring function gets the characters from a string between two specified indices.
 
  1. <!DOCTYPE html>  
  2. <html xmlns="http://www.w3.org/1999/xhtml">  
  3. <head runat="server">  
  4.        
  5. </head>  
  6. <body>  
  7.     <form id="form1" runat="server">  
  8.         <script>  
  9.             var a = "RamaSagar";  
  10.             alert(a.substring(2,5));  
  11.         </script>  
  12.     </form>  
  13. </body>  
  14. </body>  
  15. </html>  
  Output
 
 
 
toLowerCase() Function
 
This function changes the string to lower case from upper case. In the example string there are two upper case characters and by using this function all characters are changed into lowercase. 
 
  1. <!DOCTYPE html>  
  2. <html xmlns="http://www.w3.org/1999/xhtml">  
  3. <head runat="server">  
  4.        
  5. </head>  
  6. <body>  
  7.     <form id="form1" runat="server">  
  8.         <script>  
  9.             var a = "RAMASAGAR";  
  10.             alert(a.toLowerCase());  
  11.         </script>  
  12.     </form>  
  13. </body>  
  14. </body>  
  15. </html>  
 
 
 toUpperCase() Function
 
 This function converts the string to uppercase. The following is a sample example of the toUpperCase() function:
 
  1. <!DOCTYPE html>  
  2. <html xmlns="http://www.w3.org/1999/xhtml">  
  3. <head runat="server">  
  4.        
  5. </head>  
  6. <body>  
  7.     <form id="form1" runat="server">  
  8.         <script>  
  9.             var a = "ramasagar";  
  10.             alert(a.toUpperCase());  
  11.         </script>  
  12.     </form>  
  13. </body>  
  14. </body>  
  15. </html>  
 
 
Summary

In this article we learned various  functions of strings in JavaScript. In a future article we will learn more basic concepts of JavaScript.
 
Reference
 
http://www.w3schools.com/jsref/jsref_obj_string.asp  

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