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JavaScript

"undefined" shows up before the student list. What have I missed?

var students = [
  {name: "Asia", track: "Front End Development", achievements: 3100, points: 4000},
  {name: "Bien", track: "iOS", achievements: 100, points: 200},
  {name: "Bea", track: "PHP", achievements: 2100, points: 3000},
  {name: "Bella", track: "Business Development", achievements: 1100, points: 3000},
  {name: "Basil", track: "Web Design", achievements: 200, points: 200},
  {name: "Faye", track: "Ruby", achievements: 4100, points: 5000}
];

var studentName,
    track,
    achievements,
    points,
    studentList;


function print(message) {
  var outputDiv = document.getElementById("output");
  outputDiv.innerHTML = message;
  };


for (var i=0; i<students.length; i++) {
    studentName = students[i].name;
    track = students[i].track;
    achievements = students[i].achievements;
    points = students[i].points;
    studentList += "<p>Name: " + studentName + "; " + " Track: " + track + "; "+ " Achievements: " + achievements + "; " + " Points: " + points + "</br></p>";
    print(studentList);
}

I don't know why undefined is shown on the output.

undefined

2 Answers

james south
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.a{fill-rule:evenodd;}techdegree seal-36
james south
Front End Web Development Techdegree Graduate 33,258 Points

to get rid of the undefined you only need to set studentList to the empty string, since that is all you are printing in the loop. unless you initialize it to the empty string, it is nothing, it is literally undefined, so when you start tacking strings to it and print you are adding strings to undefined, so it prints undefined then the strings you added to the end. by initializing to the empty string you give it a type and thus nothing is undefined about it, you can concatenate more strings to it and everything prints as expected.

Hi james south, that worked. :) Should I do it to all the keys or just "name"? Also, what is the purpose for this? Thanks!