Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript

brandonlind2
brandonlind2
7,823 Points
Posted by brandonlind2
brandonlind2
7,823 Points

Can someone explain to me why my for in loop isn't working?

var students= [
   {
  name: "sam" ,
  track: "ios" , 
  achievements: 50 , 
  points: 300,
  },
 {
  name: "jack",
  track: "java", 
  achievements: 50 , 
  points: 200,
  },
 {
  name: "dave",
  track: "front end dev" , 
  achievements: 50 , 
  points: 600,
  }
];

for(i=0; i < student.length; i+=1;) {
student= students[i];
for(var prop in student) {
console.log(student[prop]);
  }
}

3 Answers

Sergey Podgornyy
Sergey Podgornyy
20,660 Points
Sergey Podgornyy
Sergey Podgornyy
20,660 Points

You need to delete semicolons in the first for elements, and change student.length to students.length

for(i=0; i < students.length; i+=1) {
student= students[i];
for(var prop in student) {
console.log(student[prop]);
  }
}

This code should work

Jacob Mishkin
Jacob Mishkin
23,118 Points

The only problem with this for loop is that you are not initializing the i variable. you need to add the key word var prior to i= 0;

Sergey Podgornyy
Sergey Podgornyy
20,660 Points
Sergey Podgornyy
Sergey Podgornyy
20,660 Points

As I know it's not important. Without var we just define local scope. It's more then enough for this exercise.

Jacob Mishkin
Jacob Mishkin
23,118 Points

you mean without var you define the global scope. loops do not create scope in JS.

Sergey Podgornyy
Sergey Podgornyy
20,660 Points
Sergey Podgornyy
Sergey Podgornyy
20,660 Points

Yes, sorry. You are right, global scope. But this code works fine without initialize the i variale. You can check this on JSfiddle

Neil Anuskiewicz
Neil Anuskiewicz
11,007 Points
Neil Anuskiewicz
Neil Anuskiewicz
11,007 Points

Apparently you can't use for..in when you use array iteration (See http://stackoverflow.com/questions/5263847/javascript-loops-for-in-vs-for).

As a separate matter, you might want to run your code through JSLint (http://www.jslint.com). It detects a lot of little errors. As a Treehouse student and JavaScript beginner myself, I think JSLint is going to turn out to be very useful.. :-)

I hope this helps.