Interesting JavaScript tricks

JS-tricks.js

/* Get an Array from arguments

arguments does not have a prototype link to Array.prototype, it's just array-like
(it has a length property). Use slice to get an array from arguments.

The slice() method returns a shallow copy of a portion of an array into a new array object.
arr.slice([begin[, end]])
*/
function duckCount() {
  return Array.prototype.slice.call(arguments).filter(function(obj) {
    return Object.prototype.hasOwnProperty.call(obj, 'quack')
  }).length
}