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<html><body><h1>JavaScript Global Methods</h1><h2>The isNaN() Method</h2><p>isNaN() returns true if a value is NaN:</p><p id="demo"></p><script>let result ="Is 'NaN' NaN? " + isNaN('NaN') + "<br>" +"Is NaN NaN? " + isNaN(NaN) + "<br>" +"Is undefined NaN? " + isNaN(undefined) + "<br>" +"Is null NaN? " + isNaN(null);document.getElementById("demo").innerHTML = result;</script></body></html>