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JavaScript

Posted by Antonio Ascue Avalos
Antonio Ascue Avalos
3,023 Points

Why did my variables work despite that they were not declared with var?

So here is my code https://teamtreehouse.com/workspaces/40819478#. I OVERDID IT more than necessary but just to make it more interactive for the user. I also did not include any comments so that's missing. Another thing I forgot was to DECLARE THE VARIABLES, but the program still worked. My question is WHY and what is really my undeclared variables?

Steven Parker
Steven Parker
243,266 Points
Steven Parker
Steven Parker
243,266 Points

A direct workspace URL is only temporary. To get a persistent one, create a snapshot of your workspace and post the link it makes instead.

Antony .
Antony .
2,824 Points

thanks for clarifying that Steven Parker!

3 Answers

Antony .
Antony .
2,824 Points
Antony .
Antony .
2,824 Points

Unfortunately sharing your code this way won't show for other users. Open your workspace and on the top right click on the camera icon, called a snapshot to make a reference link to your workspace.

Steven Parker
Steven Parker
243,266 Points
Steven Parker
Steven Parker
243,266 Points

Normally, JavaScript performs "implicit global declaration" on variables that are assigned without being declared. So anything you did not declare becomes a global, even if it is only used within a function.

In the "strict" mode (enabled by the "use strict"; directive), implicit declarations are not allowed, and if you forget a declaration it will cause an error.

Matthias Margot
Matthias Margot
7,236 Points
Matthias Margot
Matthias Margot
7,236 Points

Hi Antonio,

I have a link for you that could help with clarification of that (it's a bit tricky to understand and involves something called 'scope', if you've never heard this before don't worry if you don't understand it right away, took me some time to wrap my head around but it's not that scary anymore once you get the gist of it):

http://scribu.net/blog/javascript-var-keyword-for-php-developers.html