原因肯定有,不过如果你用jQuery Form Plugin的话就可以很安逸的使用了.
http://plugins.jquery.com/project/form
里面有提交file的代码,不怕麻烦的话抠出来里面的fileUpload()函数就行了.顺便贴出来
不过细节要你自己改了.
function fileUpload() {
var form = $form[0];
var opts = $.extend({}, $.ajaxSettings, options);
var id = 'jqFormIO' + (new Date().getTime());
var $io = $('<iframe id="' + id + '" name="' + id + '" />');
var io = $io[0];
var op8 = $.browser.opera && window.opera.version() < 9;
if ($.browser.msie || op8) io.src = 'javascript:false;document.write("");';
$io.css({ position: 'absolute', top: '-1000px', left: '-1000px' });
var xhr = { // mock object
responseText: null,
responseXML: null,
status: 0,
statusText: 'n/a',
getAllResponseHeaders: function() {},
getResponseHeader: function() {},
setRequestHeader: function() {}
};
var g = opts.global;
// trigger ajax global events so that activity/block indicators work like normal
if (g && ! $.active++) $.event.trigger("ajaxStart");
if (g) $.event.trigger("ajaxSend", [xhr, opts]);
var cbInvoked = 0;
var timedOut = 0;
// take a breath so that pending repaints get some cpu time before the upload starts
setTimeout(function() {
// make sure form attrs are set
var t = $form.attr('target'), a = $form.attr('action');
$form.attr({
target: id,
encoding: 'multipart/form-data',
enctype: 'multipart/form-data',
method: 'POST',
action: opts.url
});
// support timout
if (opts.timeout)
setTimeout(function() { timedOut = true; cb(); }, opts.timeout);
// add "extra" data to form if provided in options
var extraInputs = [];
try {
if (options.extraData)
for (var n in options.extraData)
extraInputs.push(
$('<input type="hidden" name="'+n+'" value="'+options.extraData[n]+'" />')
.appendTo(form)[0]);
// add iframe to doc and submit the form
$io.appendTo('body');
io.attachEvent ? io.attachEvent('onload', cb) : io.addEventListener('load', cb, false);
form.submit();
}
finally {
// reset attrs and remove "extra" input elements
$form.attr('action', a);
t ? $form.attr('target', t) : $form.removeAttr('target');
$(extraInputs).remove();
}
}, 10);
function cb() {
if (cbInvoked++) return;
io.detachEvent ? io.detachEvent('onload', cb) : io.removeEventListener('load', cb, false);
var ok = true;
try {
if (timedOut) throw 'timeout';
// extract the server response from the iframe
var data, doc;
doc = io.contentWindow ? io.contentWindow.document : io.contentDocument ? io.contentDocument : io.document;
xhr.responseText = doc.body ? doc.body.innerHTML : null;
xhr.responseXML = doc.XMLDocument ? doc.XMLDocument : doc;
xhr.getResponseHeader = function(header){
var headers = {'content-type': opts.dataType};
return headers[header];
};
if (opts.dataType == 'json' || opts.dataType == 'script') {
var ta = doc.getElementsByTagName('textarea')[0];
xhr.responseText = ta ? ta.value : xhr.responseText;
}
else if (opts.dataType == 'xml' && !xhr.responseXML && xhr.responseText != null) {
xhr.responseXML = toXml(xhr.responseText);
}
data = $.httpData(xhr, opts.dataType);
}
catch(e){
ok = false;
$.handleError(opts, xhr, 'error', e);
}
// ordering of these callbacks/triggers is odd, but that's how $.ajax does it
if (ok) {
opts.success(data, 'success');
if (g) $.event.trigger("ajaxSuccess", [xhr, opts]);
}
if (g) $.event.trigger("ajaxComplete", [xhr, opts]);
if (g && ! --$.active) $.event.trigger("ajaxStop");
if (opts.complete) opts.complete(xhr, ok ? 'success' : 'error');
// clean up
setTimeout(function() {
$io.remove();
xhr.responseXML = null;
}, 100);
};
function toXml(s, doc) {
if (window.ActiveXObject) {
doc = new ActiveXObject('Microsoft.XMLDOM');
doc.async = 'false';
doc.loadXML(s);
}
else
doc = (new DOMParser()).parseFromString(s, 'text/xml');
return (doc && doc.documentElement && doc.documentElement.tagName != 'parsererror') ? doc : null;
};
};