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 JavaScript Loops, Arrays and Objects Tracking Data Using Objects Using `for in` to Loop Through an Object's Properties

Carl Evison
Carl Evison
2,656 Points
Posted by Carl Evison
Carl Evison
2,656 Points

why does the concatenation and comma behave differently

If I use concatenation array of skills it output like this

skills: javascript,HTML,CSS

but if I use a comma instead the output is like this

skills: ["javascript", "HTML", "CSS"]

Why is that and that are the differences? do they have their own purpose

2 Answers

Jonathan Grieve
MOD
Jonathan Grieve
Treehouse Moderator 91,252 Points
Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,252 Points

It's down to the data type that is being read by the "tracking" variable prop. One is a concatenated string of characters and the other is an array of strings.

Carl Evison
Carl Evison
2,656 Points
Carl Evison
Carl Evison
2,656 Points

That makes sense. Thank you.