javascript - 如何在对象数组中找到具有最高值的对象？

Question

我有一个数组，其中包含多个名为student的对象，每个对象student都有多个属性，其中之一是名为grades的数组。

我需要创建一个函数，循环遍历学生数组并查找哪个学生对象在其成绩数组中成绩最高。

目前我能够找到最高分，但无法理解如何追溯到它属于哪个学生。

以下是该函数的片段:

function bestStudent() {
    var bestGrade = 0;
    var student;
    for(i=0; i < studentArr.length; i++) {
        var student = studentArr[i];
        grades = student.grades;
        for(g = 0; g <grades.length; g++){
            if(grades[g] > bestGrade) {
                bestGrade = grades[g];      
            }
        }

    }    
}

Answer 1

总体思路如下:您可以首先将学生数组及其成绩映射到学生数组及其最高成绩，以便于使用并避免多次查找最大成绩计算，并且然后找到最大的学生的最高成绩。

举个例子:

var students = [
  { 
    name: "Student 1",
    grades: [ 65, 61, 67, 70 ]
  },
  { 
    name: "Student 2",
    grades: [ 50, 51, 53, 90 ]
  },
  { 
    name: "Student 3",
    grades: [ 0, 20, 40, 60 ]
  }
];
 
var highestGrades = students.map(function(stud, ind) {
  // return a student's name and his highest grade (1)
  return {
    name: stud.name,
    highestGrade: Math.max.apply(Math, stud.grades) // get a student's highest grade
  };

  // or return index and use it to access original value: (2)
  // return {
  //   index: ind, 
  //   highestGrade: Math.max.apply(Math, stud.grades)
  // };

  // or return the whole student: (3)
  // return {
  //   student: stud, 
  //   highestGrade: Math.max.apply(Math, stud.grades)
  // };

  // or just add 'highestGrade' property to object without modifying
  // if it's ok for you to have intermediate properties in your object: (4)
  // stud.highestGrade = Math.max.apply(Math, stud.grades);
  // return stud;
});

// this can be done in O(n), not in O(N * logN) if required:
var bestStudent = highestGrades.sort(function(a, b) { 
  return b.highestGrade - a.highestGrade;
})[0]; // sort by highest grade desc and return the first (the best) one

// Here we have bestStudent with his name according to map function:
console.log(bestStudent.name + " has the highest score of " + bestStudent.highestGrade); // (1)
// console.log(students[bestStudent.index].name + " has the highest score of " + bestStudent.highestGrade); // (2)
// console.log(bestStudent.student.name + " has the highest score of " + bestStudent.highestGrade); // (3)
// console.log(bestStudent.name + " has the highest score of " + bestStudent.highestGrade); // (4)

您可以重写此代码，以便它返回整个学生作为结果、或其索引或其特定属性。如果您的对象可以具有额外的中间属性，您还可以将 highestGrade 属性添加到原始对象。这取决于你，这个想法不会改变:)

这段代码比较长，但是可读性强，并且让算法的思路清晰，对于初学者来说非常重要。
如果您和您的团队喜欢更短但更复杂的代码，那么您可以轻松重写它。
就像这样:

var students = [
  { 
    name: "Student 1",
    grades: [ 65, 61, 67, 70 ]
  },
  { 
    name: "Student 2",
    grades: [ 50, 51, 53, 90 ]
  },
  { 
    name: "Student 3",
    grades: [ 0, 20, 40, 60 ]
  }
];

var bestStudent = students.map(function(stud) {
  stud.highestGrade = Math.max.apply(Math, stud.grades);
  return stud;
}).sort(function(a, b) { 
  return b.highestGrade - a.highestGrade;
})[0];

console.log(bestStudent);