String Object Methods in JavaScript

RamaSagar Pulidindi
Mar 23, 2014
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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.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var a = "RamaSagar";
alert(a.indexOf('S'));
</script>
</form>
</body>
</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.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var a = "RamaSagar";
alert(a.charAt(2));
</script>
</form>
</body>
</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”.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var a = "RamaSagar";
alert(a.replace("Rama","Replaced"));
</script>
</form>
</body>
</body>
</html>

Output

substring() Function

The substring function gets the characters from a string between two specified indices.

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
</head>
<body>
<form id="form1" runat="server">
<script>
var a = "RamaSagar";
alert(a.substring(2,5));
</script>
</form>
</body>
</body>
</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.