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<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <title>Check If a String Contains a Substring in JavaScript</title> </head> <body> <script> // Sample string var str = "The quick brown fox jumps over the lazy dog." // Check if the substring exists inside the string var index = str.indexOf("fox"); if(index !== -1){ document.write("Substring found!"); } else{ document.write("Substring not found!"); } </script> </body> </html>
