javascript中兼容主流浏览器的动态生成iframe方法

function ajaxpost(formid, showid, waitid, showidclass, submitbtn, recall) {
    var waitid = typeof waitid == 'undefined' || waitid === null ? showid : (waitid !== '' ? waitid : '');
    var showidclass = !showidclass ? '' : showidclass;
    var ajaxframeid = 'ajaxframe';
    var ajaxframe = $(ajaxframeid);
    var formtarget = $(formid).target;

    var handleResult = function() {
        var s = '';
        var evaled = false;

        showloading('none');
        try {
            s = $(ajaxframeid).contentWindow.document.XMLDocument.text;
        } catch (e) {
            try {
                s = $(ajaxframeid).contentWindow.document.documentElement.firstChild.wholeText;
            } catch (e) {
                try {
                    s = $(ajaxframeid).contentWindow.document.documentElement.firstChild.nodeValue;
                } catch (e) {
                    s = '内部错误，无法显示此内容';
                }
            }
        }

        if (s != '' && s.indexOf('ajaxerror') != -1) {
            evalscript(s);
            evaled = true;
        }
        if (showidclass) {
            $(showid).className = showidclass;
            if (submitbtn) {
                submitbtn.disabled = false;
            }
        }
        if (!evaled && (typeof ajaxerror == 'undefined' || !ajaxerror)) {
            ajaxinnerhtml($(showid), s);
        }
        ajaxerror = null;
        if ($(formid)) $(formid).target = formtarget;
        if (typeof recall == 'function') {
            recall();
        } else {
            eval(recall);
        }
        if (!evaled) evalscript(s);
        ajaxframe.loading = 0;
        $('append_parent').removeChild(ajaxframe);
    };
    if (!ajaxframe) {
        try {
            ajaxframe = document.createElement('<iframe name="' + ajaxframeid + '" id="' + ajaxframeid + '"></iframe>');
        } catch (e) {
            ajaxframe = document.createElement('iframe');
            ajaxframe.name = ajaxframeid;
            ajaxframe.id = ajaxframeid;
        }
        ajaxframe.style.display = 'none';
        ajaxframe.loading = 1;
        $('append_parent').appendChild(ajaxframe);
    } else if (ajaxframe.loading) {
        return false;
    }

    _attachEvent(ajaxframe, 'load', handleResult);

    showloading();
    $(formid).target = ajaxframeid;
    $(formid).action += '&inajax=1';
    $(formid).submit();
    return false;
}