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<html><body><h2>JavaScript Classes are written in "strict mode"</h2><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 let date = new Date(); // This will work return date.getFullYear() - this.year; }}myCar = new Car("Ford", 2014);document.getElementById("demo").innerHTML ="My car is " + myCar.age() + " years old.";</script></body><!-- Mirrored from www.w3schools.com/js/tryit.asp?filename=tryjs_class_strict_mode by HTTrack Website Copier/3.x [XR&CO'2014], Wed, 21 Dec 2022 17:06:53 GMT --></html>