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JavaScript indexOf() Method

String Object Reference JavaScript String Object

Definition and Usage

The indexOf() method returns the position of the first occurrence of a specified value in a string.

This method returns -1 if the value to search for never occurs.

Syntax

string.indexOf(searchstring, start)

Parameter Description
searchstring Required. The string to search for
start Optional. The start position in the string to start the search. If omitted, the search starts from position 0


Browser Support

Internet Explorer Firefox Opera Google Chrome Safari

The indexOf() method is supported in all major browsers.


Tips and Notes

Note: The indexOf() method is case sensitive!

Tip: Also look at the lastIndexOf() method.


Examples

Example 1

Do different searches within a string:

<script type="text/javascript">

var str="Hello world!";
document.write(str.indexOf("d") + "<br />");
document.write(str.indexOf("WORLD") + "<br />");
document.write(str.indexOf("world"));

</script>

The output of the code above will be:

10
-1
6

Try it yourself »

Example 2

Differences between indexOf and lastIndexOf:

<script type="text/javascript">

var str="I love W3Schools!"

document.write("Index of first o: " + str.indexOf("o"))
document.write("<br />")

document.write("Index of last o: " + str.lastIndexOf("o"))
document.write("<br />")

document.write("Index of first 'love': " + str.indexOf("love"))
document.write("<br />")

document.write("Index of last 'love': " + str.lastIndexOf("love"))

</script>

The output of the code above will be:

Index of first o: 3
Index of last o: 13
Index of first 'love': 2
Index of last 'love': 2

Try it yourself »


String Object Reference JavaScript String Object
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