crosstab

A utility library for cross-tab communication using localStorage.

How can I get it?

crosstab is available through npm and bower and can be installed with the following command:

npm:

npm install crosstab

bower:

bower install crosstab

What is it?

crosstab is a javascript utility library for inter-tab communication on the same domain. It offers the following features:

• Tracks open tabs
• Designates a master tab and updates the master tab if it closes or times out. This is useful for maintaining a single server connection across all tabs.
• Broadcast messages to all tabs or a particular tab

Browser Compatibility

Browser	Version Tested
IE	9+
Chrome	35+
FireFox	30+
Safari	6.1+

API

Most of the time, you will only need to do two things with crosstab, set up event handlers, and fire off events.

Broadcasts

crosstab broadcasts messages like this:

crosstab.broadcast(event, data, destination);

If a destination is not specified, the message is broadcast to all tabs, including itself.

Event Handlers

crosstab registers and unregisters event handlers like this:

crosstab.on('eventName', function(message) {
    // Handle event
});

The messages received by events have the following format:

var message = {
    id: string,          // The unique ID of this message
    event: string,       // The name of the event
    data: any,           // The data passed
    destination: string, // The destination tab
    origin: string,      // The origin tab
    timestamp: number    // The time the message was created
};

The event will not fire if the destination is present and differs from the id of the current tab.

Why was it made?

I wanted to be able to have robust cross tab communication for the purpose of resource sharing (such as websockets). Though there are some libraries which have a similar goal, they all had subtle issues. This library aims to be the most correct it can be for supported browsers. This library was created with inspiration from the intercom.js library, and addresses several of it's shortcomings by dropping support for IE8 and using a lockless system that is entirely event driven. IE8 can still be used with crosstab by using the tejacques/IE8-EventListener EventListener polyfill

Contributing

Contributions are welcome and encouraged, you can contribute in several different ways, by filing issues, commenting on discussions, or contributing code.

Filing issues

Please use the issue tracker for discussions and bug reports. For bug reports, please include as much detail as possible.

These will help determine/resolve your issue:

• Clear description of the problem or unexpexted behavior
• Clear description of the expected result or output
• Steps to reproduce
• Steps you have taken to debug it yourself
• Minimal reproducible example with self contained and runnable JS code

Contributing Code

Project Workflow

We use roughly the Github Workflow. You should:

• Create an issue for the feature/bug
• Fork the project
• Create a new branch
• Commit changes
• Submit a pull request to the master branch

Tests

Tests can be run with the following command:

grunt test

• Tests must pass
• Tests should be added for each bug/feature that is added
• All tests should be self-contained
• If test is determined to be too difficult to create for an issue, there does not need to be a test for it

Getting Started

git clone https://github.com/tejacques/crosstab
cd crosstab
npm install
grunt

You can now access:

• Examples: http://localhost:9000
• Tests: http://localhost:9000/test/mocha_test.html