Array.prototype 的泛型应用分析

x = {shift:[].shift};
x.shift();
console.info(x.length);

shift is intentionally generic; this method can be called or
applied to objects resembling arrays. Objects which do not
contain a length property reflecting the last in a series of
consecutive, zero-based numerical properties may not behave
in any meaningful manner.

0

x = {};
Array.prototype.shift.call(x);
console.info(x.length);

x = function (a, b, c) {};
Array.prototype.shift.call(x);
console.info(x.length);

var args = Array.prototype.slice.call(arguments);

Array.prototype.forEach.call(arguments, function(i) {
console.info(i);
});