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<html><body><h1>JavaScript Classes uses "strict mode"</h1><p>In a JavaScript Class you cannot use variable without declaring it.</p><p id="demo"></p><script>class Car { constructor(name, year) { this.name = name; this.year = year; } age() { // date = new Date(); // This will not work const date = new Date(); // This will work return date.getFullYear() - this.year; }}const myCar = new Car("Ford", 2014);document.getElementById("demo").innerHTML ="My car is " + myCar.age() + " years old.";</script></body></html>