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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>
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</html>