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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
231,268 Points
Steven Parker
Steven Parker
231,268 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.