$.ajax 預設不支援檔案提交，

這裡提供一個form target = iframe 的非同步提交外掛

如果需要提交檔案form 需要設定屬性 enctype="multipart/form-data"，使用外掛後會自動使用target = iframe提交form

實現非同步提交，相容性好，用法簡單！

(function ($){
	/**
	 * @name from的iframe提交 v0.1
	 * @desc 主要是考慮帶file的from非同步提交
	 * @param options
	 *        	success 成功呼叫函式 success(retex,toiframe);
	 *       	error 失敗呼叫函式 error(toiframe);
	 *        	complete 完成呼叫函式 complete(toiframe,'success');
	 *        	isSubmit 是否自動提交，預設 false
	 *       	isOne 是否一次性， 預設 false
	 * @pending       isAddDiscern 是否增加請求標識(預設iframe_async=1)如果是字串新增此引數請求值為1 
	 * @example $('form#file').form_iframe({success:function (retex){alert('提交成功,'+retex)}});
	 * @author hank 
	 */
	$.fn.form_iframe = function (options){
		var my = $(this);
		var defaults = $.extend({}, $.fn.form_iframe.defaults);
		var opts = $.extend(defaults, options);
		my.each(function (){
			var target, iframe_name, toiframe,
				myform = $(this);
			if(!myform.is('form'))
				return true;
			do{
				iframe_name = 'iframe_'+((Math.random()*10000000000000000).toString()).slice(0,14);
			}while($('iframe[name="'+iframe_name+'"]').size() > 0);
			toiframe = $('<iframe form_iframe="1" name="'+iframe_name+'"></iframe>').hide();
			myform.attr('target',iframe_name);
			myform.after(toiframe);
			myform.bind('submit',function (){
				var subCou = (isNaN(parseInt($(this).attr('form_iframe-cou'))) ? 1 : (parseInt($(this).attr('form_iframe-cou'))+1));
				$(this).attr('form_iframe-cou', subCou);
				toiframe.attr('form_iframe-cou', subCou);
			});
			toiframe.data('myform',myform);
			toiframe.bind({"error.form_iframe":function (){
				if(!toiframe.is('[form_iframe-cou]')){
					return;
				}
				opts.error(toiframe);
				opts.complete(toiframe,'failure');
				_my_complete(toiframe, 'failure');
			},
			"load.form_iframe":function (){
				if(!toiframe.is('[form_iframe-cou]')){
					return;
				}
				var retdom = $(this).contents(),
					retex = $(retdom).text();
				opts.success(retex,toiframe);
				opts.complete(toiframe,'success', retex);
				_my_complete(toiframe, 'success');
			}});
			if(opts.isSubmit)
				myform.submit();
		});
		function _my_complete(iframe){
			if(opts.isOne)
				iframe.remove();
		}
		return my;
	};
	$.fn.form_iframe.defaults = {
			success: function (){},    
			error: function (){},
			complete:function (){},
			isSubmit:false,
			isOne:false
	};
})(jQuery);