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 The Build an Object Challenge, Part 2 Solution

Posted by Julia T
Julia T
2,755 Points

Is line 1's var message = ""; necessary? Or will var message; also work?

i.e Is it obligatory to assign a value (empty string in this case) to the variable message in the beginning?

var message = ''; //line 1 here
var student;

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

}
// some more code...

https://teamtreehouse.com/library/javascript-loops-arrays-and-objects/tracking-data-using-objects/the-build-an-object-challenge-part-2-solution (code around the ~2:46 minute mark)

Julia T
Julia T
2,755 Points

oh after testing a bit I think the "" is there to prevent undefined when you return the message string.

1 Answer

Steven Parker
Steven Parker
229,644 Points
Steven Parker
Steven Parker
229,644 Points

For the code shown here, the variable "message" is not needed at all and the first line can be removed.

The "message" in the function is a parameter and will be used in preference to a global by the same name, even if one exists.

But later in the video, more code is added which does use the variable, and that code concatenates strings onto it. For that reason, it's important that it be assigned with an empty string to start with. Otherwise, the word "undefined" will appear at the beginning of the concatenated string.