CommandFusion iViewer
Scripting Documentation

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Introduction to iViewer scripting

iViewer is a powerful and versatile generic home automation remote control software. Without any scripting, you can perform complex tasks like parsing data from remote systems, filling your UI elements, responding to events, sending commands, etc.

In some cases, though, you want to have more control and more flexibility over the way you respond to events, process and generate data. To this end, you can use JavaScript to drive iViewer, talk to remote systems, watch network events and perform more complex tasks than could be done with simply parsing input with regular expressions.

iViewer defines a complete set of Application Programming Interfaces (APIs) that allow your JavaScript code to interact with the software. Your JavaScript files are loaded along with your GUI, and stay in memory for as long as your GUI is opened. This means that you can create scripts that keep context data in the long run. To keep information for longer periods of time (across sessions), you can use Persistent Global Tokens (as defined in the GUI file). Since there is no actual limit to the size of the data a token can contain, you can take advantage of this to store complex structures of data that will be saved to storage and be restored the next time your GUI is loaded.

The APIs defined by iViewer allow for:

These are just the topics covered by the APIs provided by iViewer itself. Your JavaScript code can range from very simple to large and complex, from simple single file JavaScripts to complex, modular applications with reusable code modules.

To help you with developing and debugging your scripts, iViewer provides an easy to use Remote Debugger that runs in your computer's web browser. Using the Remote Debugger, you can inspect live changes to joins, connections to remote systems, see various events happening in your GUI and monitor cache status.

Fundamentals of JavaScript in iViewer

With iViewer, you write JavaScript code very much the same way than you'd write it for a web browser. Similarly to a web page, your code:

This last point is particularly important to understand when you write JavaScript code for iViewer. All the API calls that return information do so through a callback function that you provide. When the data is available, iViewer will call your callback function with the data you requested.

Load-time code execution

Similar to the way JavaScript code loads in a web page, any code at the top level of your JavaScript files (code that isn't itself enclosed in a function) is executed as soon as the script loads in iViewer. This is important, as this implies that by the time this code is executed, the iViewer environment is not fully operational yet. The only thing you can assume with certainty at startup time is that iViewer's own environment basic setup has been performed by the time your script loads, as it is being loaded prior to loading your own scripts. Consequently, the CF global variable representing the iViewer environment is guaranteed to be available at that time.

We very strongly recommend not having any code sitting at the root level of your scripts, other than code that sets up the CF.userMain function, and for code that performs module setup.

For more information about the startup mechanism, see the associated Startup Documentation.

Asynchronous code execution

Asynchronous code execution is a concept where iViewer will:

Essentially, every time you need to get information back by calling into iViewer (for example using the CF.request(), CF.getJoin(), CF.getJoins() etc. calls),

Take, for example, this code snippet:

// Get a join value, show the result
CF.log("First set s1");
CF.setJoin("s1", "Hello, world!");
CF.log("Now get s1 back");
CF.getJoin("s1", function(join, value, tokens) {
   CF.log("Join s1 is " + value);
CF.log("Change value of s1");
CF.setJoin("s1", "Another value");

Now let's look at what you can see in the Remote Debugger's log panel:

> First set s1
> Now get s1 back
> Change value of s1
> Join s1 is Hello, world!

Even though the string Join s1 is Hello, world! is correct and shows up as expected, notice how the string Change value of s1 appears before the CF.log call in the line above. Here is the flow of code execution:

JavaScript execution flow

Steps 1 through 6 are scheduled for execution in iViewer. They will start executing sequentially once your code returns to iViewer. When iViewer reaches step 4, it schedules your callback for execution, with the correct value, but the actual execution will only happen after all the outstanding calls into iViewer finish executing.

This can take some time to get comfortable with. Fundamentally, this is not very different from the way traditional JavaScript executes in a web browser, particularly when it makes requests whose result can come back at a later time.

JavaScript compatibility

Your JavaScript code is executed by your device's WebKit engine, in the context of a hidden HTML webview. This has several implications and some limitations:

This last point is important, and deserves an explanation: due to technical constraints, your JavaScript code is being run in the main thread of the application where user interface events are also processed. This means that any lengthy operation you perform in JavaScript will block the main thread (and will prevent iViewer from responding to user interaction) until your operation completes.

An additional constraint enforced by the operating system is that any bit of javascript code executed must not take longer than 10 seconds to execute. If it does, on iOS devices the operating system will kill the application, thinking the app has crashed or blocked.


One of the major issues with working on mobile platforms is the complexity of debugging code that runs on the device. For JavaScript, in particular, it is very difficult, particulary when the code runs embedded in an application.

To make debugging easier, we have implemented a Remote Debugging Monitor which serves two purpose: to provide internal information about iViewer (join states, remote systems states, etc), and to let you debug your JavaScript code as you could do for code that runs in a web page.

For in-depth information about debugging JavaScript in iViewer, please refer to the Remote Debugging Monitor documentation.

JavaScript modules

iViewer provides a mechanism allowing you to develop reusable JavaScript code modules: you can code a generic module, and reuse it in several applications without any modification.

To this end, iViewer has a loading mechanism where modules can specify a setup function. All modules have their setup function called prior to your CF.userMain function being called.

To learn more about how you can make reusable code modules for iViewer, please read the Module Development Guidelines document.