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<html>
	<head>
		<title>
			Assignment 2: GPA Calculator
		</title>
			<script type="text/JavaScript">
			var SENTINEL = 'end';
			var courseArray = new Array();
			var gradeArray = new Array();
			var avg = 0;
			var sum = 0;
			var highestGradeIndex = 0;
			var lowestGradeIndex = 0;
			var courseCode = "";
			var courseGrade = 0.0;

			function isValidCourseCode(courseCode) {
				return /[A-Z]{3}[1-9]{1}[0-9]{3}/.test(courseCode);
			}


			var i = 0;

			while (true) {
				courseCode = prompt('Enter course code:');

				if (!courseCode.localeCompare(SENTINEL)) {
					break;
				}

				while (!isValidCourseCode(courseCode)) {
					alert('The input is invalid.');
					courseCode = prompt('Input course code:');

					if (!courseCode.localeCompare(SENTINEL)) {
						break;
					}
				}

				courseGrade = parseFloat(prompt('Enter ' + courseCode + ' grade:'));

				while (!((+courseGrade >= 3 && +courseGrade <= 7) || (+courseGrade == 1.5))) {
					alert('The input is invalid.');
					courseGrade = parseFloat(prompt('Enter ' + courseCode + ' grade:'));
				}

				courseArray[i] = courseCode;
				gradeArray[i] = +courseGrade;
				i += 1;
			}


			for (i = 1; i < courseArray.length; i++) {
				if (gradeArray[i] > gradeArray[highestGradeIndex]) {
					highestGradeIndex = i;
				} else if (gradeArray[i] < gradeArray[lowestGradeIndex]) {
					lowestGradeIndex = i;
				}

				/* Calcuate GPA here as well */
				var sum = 0;

				for(var i=0; i<gradeArray.length; i++){
					sum += gradeArray[i];
				}
				if(gradeArray.length!=0){
					avg = sum/gradeArray.length;
					avg = avg.toFixed(1)
				}
			}
			var entries = courseArray.length
			var highestGradeCourse = courseArray[highestGradeIndex];
			var lowestGradeCourse = courseArray[lowestGradeIndex];

            document.writeln('<table border="1">');
			document.writeln('<tr>');
			document.write('<th>Course</th>');
			document.write('<th>Grade</th>');
			document.writeln('</tr>');
			for (i = 0; i < courseArray.length; i++) {
				document.writeln('<tr>');
				document.write('<td>' + courseArray[i] + '</td>');

				document.write('<td>' + gradeArray[i] + '</td>');
				document.writeln('</tr>');
			}
			document.writeln('</table><br />');
			document.writeln('<h6>Information</h6><br />');
				document.writeln('The number of courses entered are: ' +entries +'<br />');
				document.writeln('The highest grade achieved was for: ' +highestGradeCourse +'<br />');
				document.writeln('The lowest grade achieved was for: ' +lowestGradeCourse +'<br />');
				document.writeln('GPA: ' +avg);

			</script>

		</title>
	</head>
</html>