an ajax multipart/form-data uploader

fwajax3.js

function FwAjax3(host, cb) {
	var req = function() {
		try{ return new XMLHttpRequest();} catch(e){}
		try{ return new ActiveXObject("Msxml2.XMLHTTP.6.0") }catch(e){}
		try{ return new ActiveXObject("Msxml2.XMLHTTP.3.0") }catch(e){}
		try{ return new ActiveXObject("Msxml2.XMLHTTP") }catch(e){}
		try{ return new ActiveXObject("Microsoft.XMLHTTP") }catch(e){}
		return null;
	}(),
	boundary = function () {
		var tmp = Math.random();
		var thisDate = new Date();
		tmp = Math.abs(tmp*thisDate.getTime());
		tmp = "--------" + tmp + "--------";
		return tmp;
	}(),
	createFile = function (_field, _value, _encoding) {
		var tmp = "--" + boundary + CRLF;
		tmp += "Content-Disposition: attachment; name=\"" + _field + "\"; filename=\"" + _value.name + "\"" + CRLF;
		tmp += "Content-Type: " + _value.type + CRLF;
		tmp += "Content-Transfer-Encoding: " + _encoding + CRLF + CRLF;
		tmp += _value.data + CRLF;
//		tmp += "--" + boundary + "--" + CRLF + CRLF;
		return tmp;
	},
	createField = function (_field, _value) {
		var tmp = "--" + boundary + CRLF;
		tmp += "Content-Disposition: form-data; name=\"" + _field + "\"" + CRLF;
		tmp += "Content-Transfer-Encoding: chucked" + CRLF + CRLF;
		tmp += _value + CRLF;
//		tmp += "--" + boundary + "--" + CRLF + CRLF;
		return tmp;
	},
	fields = [],
	files = [],
	CRLF = "\r\n";
	req.onreadystatechange = function() {
		if(window.console) console.log(req.readyState);
		if(req.readyState == 4) {
			if(window.console) console.log(req.status);
			if(req.status == 200) {
				cb(req.responseText, req.responseXML);
			}
		}
	};
	this.addFile = function(_field, _value, _encoding) {
		files.push([_field, _value, _encoding]);
	};
	this.removeFile = function(_field) {
		for (var i=0; i<files.length; i++) {
			if (files[i][0] == _field) {
				files.splice(i,1);
			}
		}
	};
	this.clearFile = function() {
		files = [];
	};
	this.addField = function(_field, _value) {
		fields.push([_field, _value]);
	};
	this.removeField = function(_field) {
		for (var i=0; i<fields.length; i++) {
			if (fields[i][0] == _field) {
				fields.splice(i,1);
			}
		}
	};
	this.clearField = function () {
		fields = [];
	};
	this.send = function() {
		req.open("POST", host, true);
		var msgBody = "";
		for (var i=0; i<fields.length; i++){
			msgBody += createField(fields[i][0], fields[i][1]);
		}
		for (var i=0; i<files.length; i++){
			msgBody += createFile(files[i][0], files[i][1], files[i][2]);
		}
        msgBody += "--" + boundary + "--" + CRLF + CRLF;
		req.setRequestHeader("Content-Type","multipart/form-data; boundary="+boundary);
//		req.setRequestHeader("Transfer-Encoding", "base64");
//		req.setRequestHeader("Connection","Keep-Alive");
//		req.setRequestHeader("Content-Length",msgBody.length);
//        if(window.console) console.log('content-length: ' + msgBody.length);
		req.send(msgBody);
	};
}