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JavaScript

Posted by Ajas Sharafudeen
Ajas Sharafudeen
6,726 Points

Uncaught TypeError: Cannot read property 'name' of undefined.

In this code challenge 'The Build an Object Challenge, Part 2' , I have gone through the solution and did exactly the same as Dave did. But the error 'Uncaught TypeError: Cannot read property 'name' of undefined' has appeared eventhough the code is exactly the same.

var message = '';
var student;

function print(message) {
  var outputDiv = document.getElementById('output');
  outputDiv.innerHTML = message;
}
  for( var i=0; i<= students.length; i+=1) {
    student = students[i];
    message += '<h2>Student: ' + student.name + '</h2>';
  }
  print(message);
Linas Mackonis
Linas Mackonis
7,071 Points

Hi Ajas, your variable student is not defined. It should have an object with a name like: 

var student = {
    name: 'Ajas';
}
Ajas Sharafudeen
Ajas Sharafudeen
6,726 Points

I am working with this code and it's all clear here. I've used a new variable student = students[i]; to access the name with student variable. I cannot understand the issue here.

var students = [ 
  { 
    name: 'Dave',
    track: 'Front End Development',
    achievements: 158,
    points: 14730
  },
  {
    name: 'Jody',
    track: 'iOS Development with Swift',
    achievements: '175',
    points: '16375'
  },
  {
    name: 'Jordan',
    track: 'PHP Development',
    achievements: '55',
    points: '2025'
  },
  {
    name: 'John',
    track: 'Learn WordPress',
    achievements: '40',
    points: '1950'
  },
  {
    name: 'Trish',
    track: 'Rails Development',
    achievements: '5',
    points: '350'
  }
];

2 Answers

Linas Mackonis
Linas Mackonis
7,071 Points

Ajas, pay attention to what you wrote in the for loop condition:

i <= students.length;

students.length will give you 5 Meanwhile var i will starts to increment from 0, 1, 2, 3, 4, 6, this way you will get 6 loops and the 6th is undefined, because there are no 6 items in the student array. Your for loop condition should look like this i < students.length;

Take a look at this code: 

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

for(var i = 0; i < students.length; i += 1) {
    student = students[i];
    message += '<h2>Student: ' + student.name + '</h2>';
  }
  print(message);
Ajas Sharafudeen
Ajas Sharafudeen
6,726 Points
Ajas Sharafudeen
Ajas Sharafudeen
6,726 Points

Thanks a lot.