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JavaScript JavaScript Foundations Variables Hoisting

Fabiano Brandão
Fabiano Brandão
2,176 Points
Posted by Fabiano Brandão
Fabiano Brandão
2,176 Points

[SOLVED] Advantages of global variables

In which situations global variables are better than local scope? What are the advantages of using them over local variables?

index.html 
<!DOCTYPE html>
<html lang="en">
  <head>
    <title> JavaScript Foundations: Variables</title>
    <style>
      html {
        background: #FAFAFA;
        font-family: sans-serif;
      }
    </style>
  </head>
  <body>
    <h1>JavaScript Foundations</h1>
    <h2>Variables: Hoisting</h2>

    <script>

    function elevatorCloseButton(pushed) {

        if (pushed) {
            var status = "I'll close when I'm ready.";
        }

    }

    elevatorCloseButton(true);

    </script>
  </body>
</html>
Kristi Smythe
Kristi Smythe
10,665 Points
Kristi Smythe
Kristi Smythe
10,665 Points

Hi Fabiano,

Great question!

It's my understanding that global variables can toss you into a debugging nightmare in a complex application.

Also var is the dredd pirate 'optional' in JavaScript. Omitting var when we're creating our functions causes a variable to escape and go global, like a bubbling volcanic eruption on a 'mess up your app' spree.

This also includes not utilizing var i = 0; for your iterators in a loop. You can imagine that if you have more than one of these loopy little i suckers messing around outside their functions, it could drive you nuts trying to find out why your hard wrought masterpiece is misbehaving.

To quote a convo on this topic from Stack Overflow, "This [omitting var] is, in my opinion, one of the most dangerous issues with javascript, and should be deprecated, or at least raise warnings over warnings. The reason is, it's easy to forget var and have by accident a common variable name bound to the global object. This produces weird and difficult to debug behavior." Source: http://stackoverflow.com/questions/2485423/javascript-is-using-var-to-declare-variables-optional

Iain Simmons
Iain Simmons
Treehouse Moderator 32,305 Points

Kristi Smythe, you should include your answer as an actual answer to the question, rather than a comment, so the person asking can mark it as the 'best answer' and the question will be noted as being 'answered'... particularly when you're providing such excellent advice! :)

Marcus Parsons
Marcus Parsons
15,719 Points

I agree with Iain Simmons. Kristi Smythe that was excellent advice, and if you can, in the future, put your answer as an answer instead of a comment. But no matter, I'm going to mark this as solved since you provided such a well thought out and well spoken answer.

Fabiano Brandão
Fabiano Brandão
2,176 Points
Fabiano Brandão
Fabiano Brandão
2,176 Points

Thank you for helping me out, Kristi. =)