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<html><body><h1>JavaScript Operators</h1><h2>The in Operator</h2><p>The in operator returns true if a property is in an object.</p><p id="demo"></p><script>const person = {firstName:"John", lastName:"Doe", age:50};document.getElementById("demo").innerHTML =("firstName" in person) + "<br>" +("age" in person) + "<br>" +("address" in person);</script></body></html>