duffsDevice 高速版

function duffsDevice(items, fn) {if ('function' !== typeof(fn)) return;var iterations = items.length % 8, i = items.length - 1,callback = fn;while (iterations) {callback(items[i--]);iterations--;}iterations = Math.floor(items.length / 8);while (iterations) {callback(i--,items[i]);callback(i--,items[i]);callback(i--,items[i]);callback(i--,items[i]);callback(i--,items[i]);callback(i--,items[i]);callback(i--,items[i]);callback(i--,items[i]);iterations--;}}