Java Script Array Advanced Methods

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<h2>JavaScript Arrays</h2>

<p>The Array.findIndex() method returns the index of the first element in an array that passes a 
test (provided by a function).</p>

<p id="demo"></p>

<script>
const ages = [3, 10, 18, 20];

document.getElementById("demo").innerHTML = ages.findIndex(checkAge);

function checkAge(age) {
  return age > 18;
}
</script>

<p>The Array.find() method is not supported in Internet Explorer.</p>

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