problem in _.each function

in _.each function: 
The test for the argument "obj" to be an Array has been
if (obj.length === +obj.length)

This seems unfortunatelly not to be the best test since this
var obj = {length:1} 
is not an Array, but will be taken for one (and hence break _.each)

An alternative test criteria which would avoid this problem is:
if (Object.prototype.toString.call( obj ) === '[object Array]')