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JavaScript JavaScript Basics (Retired) Creating Reusable Code with Functions Variable Scope

John Haas
John Haas
1,756 Points
Posted by John Haas
John Haas
1,756 Points

Scope question.

I get scope of variables for the most part, but had a question. What if you declare a variable inside a function and also declare the same variable outside? What happens to the variable? For example.

var name = "Tom";

function example() { var name = "Tom"; name = "Ed";
}

alert(name);

1 Answer

Ken Alger
STAFF
Ken Alger
Treehouse Teacher
Ken Alger
Ken Alger
Treehouse Teacher

John;

Welcome to Treehouse! Let's have a look, based on your code example:

var name = "Tom";

console.log("Initial name call outside of : ", name);

function example() {    
  var name = "Tom";
    console.log("Initial name call inside function: ", name);
  name = "Ed";
    console.log("Second name call inside function: ", name);
}

console.log("Second name call outside of function - before function is called: ", name);

example();

console.log("Third name call outside of function - after function is called: ", name);

That will output to the console log:

"Initial name call outside of : " "Tom" 
"Second name call outside of function - before function is called: " "Tom"
"Initial name call inside function: " "Tom"
"Second name call inside function: " "Ed"
"Third name call outside of function - after function is called: " "Tom"

As you can see during the function declaration, nothing is actually output until the function is called later in the code. For further information I would point you to the MDN Scope Cheatsheet.

Hope it helps and happy coding,

Ken