it works consistently

main.mjs

@@ -30,32 +30,32 @@ const grades = [
 	}
 ]
 
+/**
+ * Returns the grade corresponding to mark.
+ *
+ * @param {number} input The marks out of 100.
+ * @return The corresponding grade of the marks.
+ * @customfunction
+ */
+
 function getGrade(mark){
-	if (typeof(mark) != 'number')
-	for (let i=0;i<=grades.length-1;i++){
-		const {max} = grades[i]
-		printdebug({i,max})
 
-		if (max > mark) continue
+	if (isNaN(Number(mark))) return 'Ab'
+	if (mark > 100 || mark < 0) return 'OUT OF MARK RANGE'
 
-		for (let j=i;j>0;j--) {
+	main: for (let i=0;i<grades.length;i++){
-			const {min,grade} = grades[j]
+		printdebug({i})
-		printdebug({j,min})
+		if (mark > grades[i].max) continue
-			if (mark < min) continue
+		while (grades[i].min > mark){
-			return grade
+			if (++i === grades.length) break main
+			printdebug({i})
 		}
+		return grades[i].grade
 	}
-	return 'Ab'
-	//const [{grade}] = grades.filter(({max,min}) => mark <= max && mark >= min)
-	//return grade
 }
 
 
 const grade = getGrade(argv[2])
 console.log(grade)
 
-function printdebug(text) {
+function printdebug(text){ if (DEBUG)console.error('DEBUG:',text) }
-	if (DEBUG) {
-		console.error('DEBUG:',text)
-	}
-}