想要通过使用Javascripts map，reduce，foreach，filter方法来实现功能(Want to achieve functionality by using Javascripts map,reduce,foreach,filter methods)

 请帮我写出更好的代码。 
 
 假设我有一个如下所示的JavaScript数组： 
 
var students = [
    { firstname: "stud1", lastname: "stud2", marks: "60" },
    { firstname: "stud3", lastname: "stud4", marks: "30" },
    { firstname: "stud5", lastname: "stud6", marks: "70" },
    { firstname: "stud7", lastname: "stud8", marks: "55" },
    { firstname: "stud9", lastname: "stud10", marks: "20" },
];
 
 在页面上我想分两部分显示数据：1）得分> = 40的学生2）得分<40的学生 
 
 通过使用for循环，我可以轻松完成此功能，如下所示。 
 
var data = "";var data1 = "";
for (var i = 0; i < students.length; i++ )
{
    if(students.marks >= 40){
        data += = students.firstname + " " + students.lastname; //actual data in html div tag
        ....
    }else{
            data1 += = students.firstname + " " + students.lastname;
    }
}
 
 我想通过使用map，reduce，foreach，filter等JavaScript方法来实现相同的功能。（想要提高我的JavaScript知识） 
 
 不确切知道哪种方法对此类功能有用。 
 
 使用map方法并尝试显示数据，但每个对象/数组的末尾都有一个尾随。 
 
 任何人都可以帮助/指导我编写正确的代码吗？ 

Please help me to write better code.
 
Suppose I have a JavaScript array like below:
 
var students = [
    { firstname: "stud1", lastname: "stud2", marks: "60" },
    { firstname: "stud3", lastname: "stud4", marks: "30" },
    { firstname: "stud5", lastname: "stud6", marks: "70" },
    { firstname: "stud7", lastname: "stud8", marks: "55" },
    { firstname: "stud9", lastname: "stud10", marks: "20" },
];
 
On page I want to show data in two parts, 1)Students who got marks >= 40 2)Students who got marks < 40
 
By using for loop I done this functionality easily as below. 
 
var data = "";var data1 = "";
for (var i = 0; i < students.length; i++ )
{
    if(students.marks >= 40){
        data += = students.firstname + " " + students.lastname; //actual data in html div tag
        ....
    }else{
            data1 += = students.firstname + " " + students.lastname;
    }
}
 
I want to achieve same functionality by using JavaScript methods like map, reduce, foreach, filter etc. (want to improve my JavaScript knowledge)
 
Don't know exactly which method is useful for such functionality. 
 
Used map method and tried to display data, but there is a trailing , at the end of each object/array.
 
Can anyone please help/guide me to write proper code?

原文：https://stackoverflow.com/questions/41801501