从数组中选择随机值并创建新数组

Question

I have an array, and need to pick three random values from that array. These will the be put in a new array and I will be able to see the new array on my website. I also have to make sure that no value gets picked twice.

This is what I have so far:

 var student = ["Hans","Ole","Nils","Olav","Per","Knut","Line","Pia"];
 var velg = student[Math.floor(Math.random() * student.length)];

I'm thinking I should add an id to my HTML, so the new array will show on my website, but I'm not sure about the rest.

Answer 1

First sort it randomly and then get first three:

student
   .sort(function(){
       return Math.random() - 0.5;
     })
   .slice(0,3)

Since Math.random() returns random value between 0 and 1, while sort expects values to be positive or negative to determine order we, we need to subtract 0.5 to make those negatives possible.

Answer 2

You could try something like this in a loop

var students = ["Hans","Ole","Nils","Olav","Per","Knut","Line","Pia"];
var randomStudents = [];
for(var i = 0; i < 3; i++) {
    var velg = student[Math.floor(Math.random() * students.length)];
    randomStudents.push(velg);
}

Note that this can add duplicate students to the array. You should check if student is already in the array and try again.

Keyword for that would be recursion.

https://www.codecademy.com/courses/javascript-lesson-205/0/1