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<html>
<script>
	class User{

		constructor(firstname,lastname)
		{
			this.firstname = firstname;
			this.lastname = lastname;

		}
		getName()
		{
			this.firstname = prompt("Enter your first name:","")	;
			this.lastname = prompt("Enter your last name:","");
	        }

	showName()
	{
		if(this.firstname.indexOf(' ') <=0 || this.lastname.indexOf(' ') <=0 )
		{
			alert(`Hello ${this.firstname} ${this.lastname}`)
			return;
		}

	}

}

var obj1 = new User();
obj1.getName();
obj1.showName();
</script>
</html>