如何判断多个iframe是否加载完成，加载完成后调用打印窗口

[yan雨天青色]

我用了两种方法，如下：都没有实现，却也没有报错

    function print(){
        debugger;
        var iframeLength = document.getElementsByTagName("iframe").length;
        var iframe_start = 0;
        $('iframe').each(function () {
            var src = $(this).attr('src');
            $(this).onload = function () {
                iframe_start++;
                console.info(iframe_start);
                if (iframe_start == iframeLength) {
                    window.print();
                }
            }
        });
    }
    function print2() {
        debugger;
        var iframes = document.getElementsByTagName("iframe");
        for (var i = 0; i < iframes.length; i++) {
            var iframeId = iframes[i].id;
            var currentIframe = document.getElementById(iframeId);
            if (currentIframe.attachEvent) {
                currentIframe.attachEvent("onload", function () {
                    // 等待iframe加载完成
                });
                continue;
            } else {
                currentIframe.onload = function () {
                    window.print();// iframe加载完成
                }
            }
        }

    }