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<html><body><h1>JavaScript Arrays</h1><h2>findIndex()</h2><p>findIndex() returns the index of the first element 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>findIndex() is not supported in Internet Explorer.</p></body><!-- /jsref/tryit.asp?filename=tryjsref_findindex </html>