MultipartForm.js

var MultipartForm = function () {

	var boundary = '------------------------------' + Date.now(), string = '--' + boundary + '\r\n';

	this.addVariable = function ( name, value ) {

		string += 'Content-Disposition: form-data; name="' + name + '"\r\n';
		string += 'Content-Type: text/plain\r\n';
		string += '\r\n' + value + '\r\n';
		string += '--' + boundary + '\r\n';

	};

	this.addFile = function ( name, filename, filetype, data ) {

		string += 'Content-Disposition: form-data; name="' + name + '"; filename="' + filename + '"\r\n';
		string += 'Content-Type: ' + filetype + '\r\n';
		string += '\r\n' + data + '\r\n'; 
		string += '--' + boundary + '\r\n';

	};

	this.getBoundary = function () {

		return boundary;

	};

	this.getString = function () {

		return string;

	};

	this.getBuffer = function () {

		return new Uint8Array( Array.prototype.map.call( string, function ( x ) { return x.charCodeAt( 0 ) & 0xff; } ) ).buffer;

	};

}