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<!DOCTYPE html> <html> <body> <h2>JavaScript Array.findIndex()</h2> <p id="demo"></p> <script> const numbers = [4, 9, 16, 25, 29]; document.getElementById("demo").innerHTML = "First number over 18 has index " + numbers.findIndex(myFunction); function myFunction(value, index, array) { return value > 18; } </script> </body> </html>