To get the first index of an occurrence of the specified value in a string, use the JavaScript indexOf() method.
Example
You can try to run the following code to get the first index −
<html> <head> <title>JavaScript String indexOf() Method</title> </head> <body> <script> var str = new String( "Learning is fun! Learning is sharing!" ); var index = str.indexOf( "Learning" ); document.write("First index of string Learning :" + index ); </script> </body> </html>