Backbone.js doesn't recognize a variable

Question

I'm trying to use Backbone.js in a web page.

When I link to the .js file for version 0.9.9 I get the following error at line 225.

 TypeError _ is undefined
 _.extend(Backbone,Events);

However, _ is defined at line 40

  var _ = root._;

And that variable declaration isn't inside a loop or conditional statement.

Why doesn't line 225 recognize what line 40 declared?

Answer 1

Backbone.js is dependent on Underscore.js