var objectPoolFactory = function (createObjFn) {

            var objectPool = [];

            return {

                create: function () {

                    var obj = objectPool.length === 0 ? createObjFn.apply(this, arguments) : objectPool.shift();

                    return obj;

                },

                recover: function (obj) {

                    objectPool.push(obj);

                }

            };

        };

        var iframeFactory = objectPoolFactory(function () {

            var iframe = document.createElement('iframe');

            document.body.appendChild(iframe);

            iframe.onload = function () {

                iframe.onload = null;

                iframeFactory.recover(iframe);

            };

            return iframe;

        });

        var iframe1 = iframeFactory.create();

        iframe1.src = 'http://www.baidu.com';

        var iframe2 = iframeFactory.create();

        iframe2.src = 'http://www.sina.com';

        setTimeout(function () {

            var iframe3 = iframeFactory.create();

            iframe3.src = 'http://www.qq.com';

        }, 10000);