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JavaScript

Posted by Martinus Lukas
Martinus Lukas
Courses Plus Student 3,023 Points

Question for :: Build a Quiz Challenge, Part 2 Solution (JavaScript)

Hey, I finish my challenge. But is something wrong with my code, when I run my code is run well, but i have message "undefined". Can someone review it, thanks!

//pertanyaaan disimpan dalam array

var tanya = [
["Siapa nama presiden Indonesia?", "JOKOWI"],
["Siapa manusia pertama yang berhasil mendarat di bulan?","Neil"],
["Siapa nama presiden wanita pertama di Indonesia","Megawati"]    
];

var benar = [];
var salah = [];

//set pertanyaan dengan loop
var no = 0;

while(no < tanya.length) 
{
  var jawab = prompt(tanya[no][0]);
  if(jawab === tanya[no][1]) 
  {
    benar.push(tanya[no][0]);
  } else 
  {
    salah.push(tanya[no][0]);
  }
  no++;

}

//fungsi tampil data yang benar
function tampilData() 
 {
var html;
var no = 0;   
html += "<p>Pertanyaan benar yang anda jawab sebanyak ("+benar.length+")</p>";
html += "<ul>";
   if(benar.length > 0) 
   {
for(no; no < benar.length; no++) 
    {

      html += "<li>"+benar[no];
      html += "</li>";

    }
   }else 
   {
      html += "<li>Upps, sepertinya tidak ada jawaban yang benar!</li>";
   }

   html += "</ul>";

html += "<p>Pertanyaan salah yang anda jawab adalah ("+salah.length+")</p>";
   html += "<ul>";
   if(salah.length > 0)
   {
     for(var no=0; no < salah.length; no++)
     {
       html += "<li>"+salah[no]+"</li>";
     }                     
   }else 
   {
     html += "<li>Uups, sepertinya tidak ada yang salah! <strong>SELAMAT</strong></li>"
   }

   html += "</ul>";

      return html;

 }

function print(message) {
  document.write(message);
}


print(tampilData());

```</script>

#sorry, that code is write in Indonesia language ^-^

2 Answers

Benjamin Barslev Nielsen
Benjamin Barslev Nielsen
18,958 Points
Benjamin Barslev Nielsen
Benjamin Barslev Nielsen
18,958 Points

undefined comes from:

var html;

this statement is equal to:

var html = undefined;

And when you concatenate the value undefined with a String, the undefined value is coerced into the string "undefined", so particularly this means:

undefined + "someString" Evaluates to "undefinedsomeString"

Therefore the solution should be to initialize the html variable to the empty String instead:

var html = "";

Hope this helps

Martinus Lukas
PLUS
Martinus Lukas
Courses Plus Student 3,023 Points
Martinus Lukas
Martinus Lukas
Courses Plus Student 3,023 Points

Ohh, thanks for replay Sir, it work! xD