Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

JavaScript

Audra Ogilvy
Audra Ogilvy
3,142 Points

Using the var keyword versus just using =

In JavaScript, is there a difference between a variable created using the var keyword, and a variable created just with the equals operator? In other words, is this: var guess = false different than this: guess = false ?

1 Answer

Steven Parker
Steven Parker
221,328 Points

It depends on where it is done.

In global scope, they are the same. But in a function, "var" creates a variable limited to the scope of the function, but an implicit declaration creates (or alters) a global variable.

But implicit declarations are not considered good programming practice, and when the system is in "strict" mode, they are not allowed at all and cause an error.