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

Catelinn Xiao
Catelinn Xiao
4,139 Points
Posted by Catelinn Xiao
Catelinn Xiao
4,139 Points

Why can't I use for in loop for student objects?

Can I use for in loop to access the properties of each student object like this?

for ( var i = 0; i < students.length; i += 1 ) {

student = students[i];

for ( var key in student ) { message += "<p>" + student.key + "</p>"; } }

I tried, it showed "undefined" in the output. Why?

2 Answers

Javier Mera
Javier Mera
16,472 Points
Javier Mera
Javier Mera
16,472 Points

Because key represents each property in the object, you have to use bracket notation to access each student object, in the array. So for example, students[0][key].Name, would give you the Name of the first student in the array.

So in your case, you'd have to use student[key], to access a student in each iteration.

for ( var key in student ) { message += "<p>" + student[key] + "</p>"; } }

Rick Buffington
Rick Buffington
8,146 Points
Rick Buffington
Rick Buffington
8,146 Points

I'm thinking that you probably can't use student.key - you would have to use just key because student doesn't contain a field or method called key. key is the iterator for your foreach loop.