what is this underscore.js “safe reference” code doing?

Question

I\'m learning Backbone, which uses Underscore.

In some examples, I see initialization code to create an empty array of children like this:

// inside          


        

Answer 1

From http://underscorejs.org/#chaining

You can use Underscore in either an object-oriented or a functional style, depending on your preference. The following two lines of code are identical ways to double a list of numbers.

_.map([1, 2, 3], function(n){ return n * 2; }); // Functional style
_([1, 2, 3]).map(function(n){ return n * 2; }); // OO style

So when using the OO style, the _ is used as a constructor function. Without the first two lines in the constructor function that "Creates a safe reference to the Underscore object" you would have to use the new keyword, as follows

new _([1, 2, 3]).map(function(n){ return n * 2; });

Now you don't :)