xx: Object Locking for JavaScript

> It's what you need when you need it, but you have to wait in line to get it.

xx simplifies the synchronization of data objects between concurrent tasks.

#### Installation

- Node.JS: npm install xx
- Browsers: Add lib/xx.js to your HTML page.

Intro

Here's a brief example that shows how to use xx:

``javascript
var xx = require('xx'); // import xx

var config = {}; // Have some data to guard

config.xx = xx(); // Create a lock object

// Acquire lock on the object with an async callback:
config.xx(
function() {
// Invoked when the object is available

// Call without a function when you want to unlock the object:
config.xx();
}
);
`

Usage with Async Libraries

Here's a brief example that shows how it can be used with an async library (such as ff):

`javascript
var xx = require('xx'); // import xx
var ff = require('ff'); // Use ff for a demo

var config = {
fileA: "A.txt",
fileB: "B.txt"
}; // Have some data to guard

config.xx = xx(); // Create a lock object

var f = ff(this, function () {

// Added: Wait to acquire lock
config.xx(f());

}, function () {
fs.readFile(config.fileA, f());
fs.readFile(config.fileB, f());
}, function (fileA, fileB) {
concatFiles(fileA, fileB, f());
}, function (result) {
config.result = result.toUpperCase();

// Added: Done with lock here!
config.xx();

f();
}).cb(cb);
``