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JavaScript JavaScript Loops, Arrays and Objects Tracking Data Using Objects The Build an Object Challenge, Part 2

Michael Lo
Michael Lo
2,785 Points
Posted by Michael Lo
Michael Lo
2,785 Points

Wondering why this code prints the number '4' to the document. 

//data structure 
//name, track, achievments(num), points(num)

var students = [
  {name: 'David', track: 'IOS', achievments: 10, points: 200},
  {name: 'Kate', track: 'JS, IOS', achievments: 20, points: 1200},
  {name: 'Emily', track: 'Windows', achievments: 30, points: 2200},
  {name: 'joan', track: 'Ruby', achievments: 40, points: 2030},
  {name: 'Ben', track: 'IOS', achievments: 50, points: 2001},
];


  //print function

  function print(message) {
    var div = document.getElementById('output');
    div.innerHTML = message; 
  }


  //loop the student records to the page. 

  for (var key in students) {
     print(key, ', ', students[key]);
  }
Jacob Mishkin
Jacob Mishkin
23,117 Points

edited code for formating

Tolumi Adamson
seal-mask
.a{fill-rule:evenodd;}techdegree
Tolumi Adamson
Front End Web Development Techdegree Student 11,645 Points
Tolumi Adamson
.a{fill-rule:evenodd;}techdegree
Tolumi Adamson
Front End Web Development Techdegree Student 11,645 Points

Yeah, that drove me crazy for a bit. I believe the problem is that you are using an object loop to try and access an array. I might be wrong, but that is what I figure. to access an array, you generally need to use the array name plus the location of the item you are trying to access i.e. students[0]. whereas using the for in loop, you are trying to access it in a different manner. I actually had to use a regular for loop to first try and access the array itself, then a for in loop to access the object within the array. my code looked something like this

for (var i=0; i < students.length; i += 1 ) {
  for (var key in students[i]) {
    html += key + ':' + students[i].key + '<br><br>';
  }
}

1 Answer

jcorum
jcorum
71,830 Points
jcorum
jcorum
71,830 Points

Set this up in my IDE. This index.html file:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Students</title>
  <link rel="stylesheet" href="css/styles.css">
</head>
<body>
<h1>Students</h1>
<div id="output">

</div>
<script src="js/students.js" type="text/javascript"></script>
</body>
</html>

and this students.js file:

//data structure //name, track, achievments(num), points(num)

var students = [ {name: 'David', track: 'IOS', achievments: 10, points: 200}, {name: 'Kate', track: 'JS, IOS', achievments: 20, points: 1200}, {name: 'Emily', track: 'Windows', achievments: 30, points: 2200}, {name: 'joan', track: 'Ruby', achievments: 40, points: 2030}, {name: 'Ben', track: 'IOS', achievments: 50, points: 2001}, ];

//print function

function print(message) { 

 var div = document.getElementById('output'); div.innerHTML = message; }

//loop the student records to the page.

 for (var key in students) {
                print(key, ', ', students[key]);
 }

 print("Hello");

and it printed Hello.

Not sure how you were calling the print() function in your html, but everything seems to be working fine. I thought at first that perhaps you were asking for the value of one of the keys in the data structure, but since none is 4, it must be something else.

Happy coding!