Create getAllStudentGrades.js

getAllStudentGrades.js

@@ -0,0 +1,40 @@
+let grades = [
+  { student: "a", grade: 90 },
+  { student: "b", grade: 80 },
+  { student: "a", grade: 95 },
+  { student: "a", grade: 91 },
+];
+
+function getAllStudentGrades(studentList, grades) {
+  let allStudentsGrades = [];
+  let student2grades = {};
+
+  // generate student2grades map
+  for (let i = 0; i < grades.length; i++) {
+    let student = grades[i].student;
+    let grade = grades[i].grade;
+
+    if (student2grades[student] === undefined) {
+      student2grades[student] = [grade];
+    } else {
+      let currentStudentGradesLength = student2grades[student].length;
+      student2grades[student][currentStudentGradesLength] = grade;
+    }
+  }
+
+  // reformat map to desired output
+  // [ { student: "a", grade: [90, 95, 91] }, { student: "b", grade: [80] } ]
+
+  for (let i = 0; i < studentList.length; i++) {
+    let student = studentList[i];
+    let grades = student2grades[student];
+    allStudentsGrades[allStudentsGrades.length] = {
+      student: student,
+      grade: grades,
+    };
+  }
+
+  return allStudentsGrades;
+}
+
+console.log(getAllStudentGrades(["a", "b"], grades)); // ==>  [ { student: "a", grade: [90, 95, 91] }, { student: "b", grade: [80] } ]