Language - JavaScript: Difference between revisions

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<metadesc>Communicate with sensors, controllers and relays with Phidgets! Our JavaScript API supports Node.js and Browsers.</metadesc>
[[Category:Language]]
[[Category:Language]]
__TOC__
__TOC__
Line 6: Line 7:


*{{Phidget22API}} (Select JavaScript from drop-down menu)
*{{Phidget22API}} (Select JavaScript from drop-down menu)
=== Libraries ===
*'''Browser''': [{{SERVER}}/downloads/phidget22/libraries/any/Phidget22JavaScript.zip JavaScript Library Download]
*'''Node.js''': npm install phidget22


=== Example Code ===
=== Example Code ===


*{{SampleCode|JavaScript|JavaScript Examples (Node.js)}}
*[{{SERVER}}?view=code_samples&lang=JavaScript&os=Nodejs JavaScript Examples (Node.js)]
*[{{SERVER}}/downloads/phidget22/tools/any/Phidget22JavaScriptControlPanel.zip Javascript Examples (HTML)]
*[{{SERVER}}?view=code_samples&lang=JavaScript&os=Browser JavaScript Examples (Browser)]
 
=== Tools ===
 
*[{{SERVER}}/downloads/phidget22/tools/any/Phidget22JavaScriptControlPanel.zip JavaScript Control Panel Source]


=== Libraries ===
=== OS Libraries ===


*[{{SERVER}}/downloads/phidget22/libraries/any/Phidget22JavaScript.zip JavaScript Library Download]
{{AllQuickDownloads}}
{{AllQuickDownloads}}


Line 20: Line 29:
Welcome to using Phidgets with JavaScript! By using JavaScript, you will have access to the complete {{Phidget22API}}, including events. We also provide example code in JavaScript for all Phidget devices.
Welcome to using Phidgets with JavaScript! By using JavaScript, you will have access to the complete {{Phidget22API}}, including events. We also provide example code in JavaScript for all Phidget devices.


If you are developing for Windows, keep reading. Otherwise, select your operating system to jump ahead:
=== Version Change ===
*[[#macOS | macOS]]
'''Note:''' The Phidgets JavaScript library has been bumped to version 2.x.x following a rewrite. The version 2 API is mostly identical to version 1, but does have some breaking changes. It is highly recommended that any code written against version 1 be updated to version 2, as version 1 is considered unstable.
*[[#Linux | Linux]]
 
== Phidget Network Server ==
The JavaScript library requires the [[Phidget Network Server]]. Start by configuring the server for your OS:


== Windows ==
* [[OS - Windows#Phidget Network Server|Windows]]
{{Windows_Languages}}
* [[OS - OS X#Phidget Network Server|macOS]]
* [[OS - Linux#Phidget Network Server|Linux]]
* [[OS - Phidget SBC#Phidget Network Server|PhidgetSBC]]


===Browser===
The Phidget Server includes a built-in Webserver. This must be enabled when using the JavaScript library in browser, but can be left disabled when using the library from Node.js.
====Use Our Examples====
One of the best ways to start programming with Phidgets is to use our example code as a guide. Our browser examples are graphical and are installed with the Phidget libraries. In order to check them out, first open the Phidget Control Panel and navigate to the Network Server tab:
[[File:Windows_networkserver.PNG|link=|center]]


The Phidget Server Webserver can be used to serve files - such as the Phidget JavaScript library, or your own projects. By default, it serves the JavaScript control panel files. The main purpose of the Webserver is to support a Websockets connection for the Browser library - because regular sockets cannot be used in Browser. The Node.js library uses raw sockets to connect to the Phidget Server, and so does not require the Webserver or Websockets.


Next, make sure the Webserver is enabled (''Enabled'' checkbox in ''Webserver'' section), and start the Phidget Network Server by clicking on the ''Start'' button at the bottom of the window. Click on the hyperlink as shown in the image below (or navigate to http://localhost:8989):
== JavaScript Control Panel ==
[[File:Javascript_windows_localhost.png|link=|center]]
The JavaScript control panel is a Browser version of our Phidget control panel. This can be used to view and control all Phidgets attached to a Phidget server. The JavaScript control panel is installed by default on Windows, macOS and PhidgetSBC. You can also download the source [{{SERVER}}/downloads/phidget22/tools/any/Phidget22JavaScriptControlPanel.zip here].


Make sure the Phidget Server - Webserver is enabled, and running, then navigate to http://localhost:8989. You will now see a program written with JavaScript/HTML that mimics the Phidget Control Panel. It will show all the Phidgets attached to your machine. By double-clicking on the Phidgets, and example will launch.


You will now see a program written with JavaScript/HTML that mimics the Phidget Control Panel. It will show all the Phidgets attached to your machine. By double-clicking on the Phidgets, and example will launch:
[[File:Javascript_windows_controlpanel.png|link=|center]]
[[File:Javascript_windows_controlpanel.png|link=|center]]


== Browser ==
=== Use Our Examples ===
One of the best ways to start programming with Phidgets is to use our example code as a guide. Our browser examples are available [{{SERVER}}?view=code_samples&lang=JavaScript&os=Browser here].


To view the source code that drives the examples, navigate to the following location:
=== Write Your Own Code ===
*C:/Program Files/Phidgets/Phidget22/html
 
 
[[File:Javascript_windows_filelocation.png|link=|center]]
 
 
Here you can view the code that was written to create the main webpage as well as all of the examples.
 
====Write Your Own Code====
Let's start by writing a simple HTML page that makes a dynamic list of attached Phidgets visible to the user.  
Let's start by writing a simple HTML page that makes a dynamic list of attached Phidgets visible to the user.  
We will be using the JavaScript library [https://jquery.com/download/ jQuery] in these examples. jQuery is not required in order to use Phidgets, however, it will make it easier for us to access elements on an HTML page.  
We will be using the JavaScript library [https://jquery.com/download/ jQuery] in these examples. jQuery is not required in order to use Phidgets, however, it will make it easier for us to access elements on an HTML page.  


To start, create a new empty folder.


To start, create a new folder that looks like this:
Next, download the latest JavaScript browser library from [{{SERVER}}/downloads/phidget22/libraries/any/Phidget22JavaScript.zip here] and copy the files into the folder.
[[File:Javascript_windows_folderlibraries.png|link=|center]]
 
 
The referenced libraries are installed with the Phidget libraries and can be found at the following location:
*C:/Program Files/Phidgets/Phidget22/html
 


Next, create a file called ''index.html'' and copy the following code into it (Note: if you have newer JavaScript libraries, modify the code below to match your version numbers):
Next, create a file called ''index.html'' and copy the following code into it (Note: if you have a newer jQuery, modify the code below to match your version):


<syntaxhighlight lang=javascript>
<syntaxhighlight lang=javascript>
Line 69: Line 69:
<html>
<html>
<head>
<head>
<title>Javascript Test Program</title>
    <title>Phidget Manager</title>
<script src="jquery-2.1.4.min.js"></script>
    <script src="jquery-2.1.4.min.js"></script>
<script src="sha256.js"></script>
    <script src="sha256.min.js"></script>
<script src="jphidgets22.1.0.0.min.js"></script>
    <script src="phidget22.min.js"></script>
 
    <script>
<script>
        $(document).ready(function() {
 
            var conn = new phidget22.Connection(8989, 'localhost');
$(document).ready(function () {
var conn = new jPhidgets.Connection('ws://' + window.location.host + '/phidgets', { name: window.location.host });
 
conn.connect().then(function () {
console.log('connected');
}).catch(function (err) {
alert('failed to connect to server:' + err);
});;
 
conn.onattach = function(dev) {
$('#list').append(new Option(dev.name,dev.phid));
}


conn.ondetach = function(dev) {
            conn.connect().then(function() {
$("#list option[value='" + dev.phid + "']").remove();
                console.log('connected');
}
            }).catch(function(err) {
});
                conn.delete();
                alert('failed to connect to server:' + err);
            });


</script>
            var man = new phidget22.Manager({
                onDeviceAttach: function(dev) {
                    $('#list').append(new Option(dev.getDeviceName(), dev.getKey()));
                },
                onDeviceDetach: function(dev) {
                    $("#list option[value='" + dev.getKey() + "']").remove();
                }
            });
            man.open();
        });
    </script>
</head>
</head>


<body>
<body>
<label> Attached Phidgets: </label>
    <label> Attached Phidgets: </label>
<div>
    <div>
<select multiple id="list" style="width: 500px;"></select>
        <select multiple id="list" style="width: 500px; height: 200px"></select>
</div>
    </div>
</body>
</body>
</html>
</html>
</syntaxhighlight>
</syntaxhighlight>


After copying the code above into your ''index.html'' file, your folder should look like this:
This code uses the [[Phidget Manager]] to list any Phidget accessible from your computer (either directly via USB or indirectly over the network).  
[[File:Javascript windows folder.png|link=|center]]
 
 
Next, open the Network Server tab in the Phidget Control Panel and modify the Webserver ''Docroot'' to your folders location:
[[File:Javascript_windows_docrootchange.png|link=|center]]
 


Finally, click on the hyperlink to see the example (or navigate to http://localhost:8989):
Finally, double click index.html to open it in a browser. You should see something like this:
[[File:Javascript_windows_example.png|link=|center]]
[[File:Javascript_windows_example.png|link=|center]]


Open the developer console to get a better idea what is going on:
Open the developer console to get a better idea what is going on:
[[File:Javascript_windows_devconsole.png|link=|center]]  
[[File:Javascript_windows_devconsole.png|link=|center]]  


For information about the Node.js examples, keep reading. Otherwise, skip ahead to the [[#Edit the Examples | edit the examples]] section located below.
For information about the Node.js examples, keep reading. Otherwise, skip ahead to the [[#Edit the Examples | edit the examples]] section located below.


 
== Node.js ==
===Node.js===
=== Use Our Examples ===
====Use Our Examples====
One of the best ways to start programming with Phidgets is to use our example code as a guide. In order to run the examples, you will need to download and install [https://nodejs.org/ Node.js].  
One of the best ways to start programming with Phidgets is to use our example code as a guide. In order to run the examples, you will need to download and install [https://nodejs.org/ Node.js].  


Now that you have Node.js installed, select an example that will work with your Phidget:
Now that you have Node.js installed, select an example that will work with your Phidget:
*{{SampleCode|JavaScript|JavaScript Examples}}
*[{{SERVER}}?view=code_samples&lang=JavaScript&os=Nodejs JavaScript Examples (Node.js)]
 
 
Next, navigate to the Network Server tab in the Phidget Control Panel and press the ''Start'' button after ensuring the Webserver is enabled (''Enabled'' checkbox in ''Webserver'' section).
[[File:Windows_networkserver.PNG|link=|center]]
 


Navigate to the example folder that you previously downloaded, open the command prompt at this location and enter the following command:
Navigate to the example folder that you previously downloaded, open the command prompt at this location and enter the following command:
Line 145: Line 129:


[[File:Javascript_windows_npmupdate.png]]
[[File:Javascript_windows_npmupdate.png]]


Next, enter the following command to run the example (replacing Accelerometer with your example name):
Next, enter the following command to run the example (replacing Accelerometer with your example name):
Line 152: Line 135:
</syntaxhighlight>
</syntaxhighlight>
[[File:Javacsript_windows_nodeexample.png|link=|center]]
[[File:Javacsript_windows_nodeexample.png|link=|center]]
You should now have the example up and running. When you are ready, the next step is [[#Edit the Examples | editing the examples]].
You should now have the example up and running. When you are ready, the next step is [[#Edit the Examples | editing the examples]].
==macOS==
=== Browser Example===
====Use our examples====
One of the best ways to start programming with Phidgets is to use our example code as a guide. Our browser examples are graphical and are installed with the Phidget libraries. In order to check them out, first open the Phidget Control Panel and navigate to the Network Server tab:
[[File:Macos_networkserver_run.png|link=|center]]
Next, make sure the Webserver is enabled (''Enabled'' checkbox in ''Webserver'' section), and start the Phidget Network Server by clicking on the ''Start'' button at the top of the window. A button labelled ''View in Browser...'' will appear. Click on it now (or navigate to http://localhost:8989).
[[File:Javascript_macos_viewinbrowswer.png|link=|center]]
You will now see a program that mimics the Phidget Control Panel (and was written entirely with JavaScript/HTML). It will show all the Phidgets attached to your machine. By double-clicking on the Phidgets, and example will launch:
[[File:Javascript_macos_browserexample.png|link=|center]]
To view the source code, navigate to the following location:
*/Library/Application Support/Phidgets/Phidget22NetworkServer/html
[[File:Javascript_macos_filelocation.png|link=|center]]
Here you can view the code that was written to create the main webpage as well as all of the examples.
====Write Your Own Code====
Let's start by writing a simple HTML page that makes a dynamic list of attached Phidgets visible to the user.
We will be using the JavaScript library [https://jquery.com/download/ jQuery] in these examples. jQuery is not required in order to use Phidgets, however, it will make it easier for us to access elements on an HTML page.
To start, create a new folder that looks like this:
[[File:Javascript_macos_folderlibraries.png|link=|center]]
As stated above, you must download the jQuery library. The rest of the libraries are installed with the Phidget libraries and can be found at the following location:
*C:/Program Files/Phidgets/Phidget22/html
Next, create a file called ''index.html'' and copy the following code into it (Note: if you have newer JavaScript libraries, modify the code below to match your version numbers):
<syntaxhighlight lang=javascript>
<!DOCTYPE html>
<html>
<head>
<title>Javascript Test Program</title>
<script src="jquery-2.1.4.min.js"></script>
<script src="sha256.js"></script>
<script src="jphidgets22.1.0.0.min.js"></script>
<script>
$(document).ready(function () {
var conn = new jPhidgets.Connection('ws://' + window.location.host + '/phidgets', { name: window.location.host });
conn.connect().then(function () {
console.log('connected');
}).catch(function (err) {
alert('failed to connect to server:' + err);
});;
conn.onattach = function(dev) {
$('#list').append(new Option(dev.name,dev.phid));
}
conn.ondetach = function(dev) {
$("#list option[value='" + dev.phid + "']").remove();
}
});
</script>
</head>
<body>
<label> Attached Phidgets: </label>
<div>
<select multiple id="list" style="width: 500px;"></select>
</div>
</body>
</html>
</syntaxhighlight>
After copying the code above into your ''index.html'' file, your folder should look like this:
[[File:Javascript_macos_folder.png|link=|center]]
Next, open the Network Server tab in the Phidget Control Panel and modify the Webserver ''Docroot'' to your folders location:
[[File:Javascript_macos_docrootchange.png|link=|center]]
Finally, click on the hyperlink (or navigate to http://localhost:8989) to see the example:
[[File:Javascript_macos_example.png|link=|center]]
Open the developer console to get a better idea what is going on:
[[File:Javascript_macos_devconsole.png|link=|center]]
For information about the Node.js example, keep reading. Otherwise, skip ahead to the [[#Edit the Examples | edit the examples]] section located below.
===Node.js===
====Use Our Examples====
One of the best ways to start programming with Phidgets is to use our example code as a guide. In order to run the examples, you will need to download and install [https://nodejs.org/ Node.js].
Now that you have Node.js installed, select an example that will work with your Phidget:
*{{SampleCode|JavaScript|JavaScript Examples}}
Next, make sure the Phidget Network Server is running and the Webserver is enabled. Do this by navigating to the Network Server tab in the Phidget Control Panel and press the ''Start'' button at the top of the window (after ensuring the Webserver is enabled):
[[File:Macos_networkserver_run.png|link=|center]]
Navigate to the example folder that you previously downloaded, open the command prompt at this location and enter the following command:
<syntaxhighlight lang='bash'>
sudo npm update
</syntaxhighlight>
[[File:Javascript_macos_npmupdate.png ‎]]
Next, enter the following command to run the example (replacing Accelerometer with your example name):
<syntaxhighlight lang='bash'>
node Accelerometer localhost
</syntaxhighlight>
[[File:Javascript_macos_nodeexample.png|link=|center]]
You should now have the example up and running. When you are ready, the next step is [[#Edit the Examples | editing the examples]].
== Linux ==
=== Browser Example ===
Download our Javascript libraries [[#Quick Downloads|here]] and follow the instructions in the README to get in-browser Javascript running.
=== node.js ===
node.js is a Javascript runtime that will allow us to run Javascript code via the terminal. Download the latest version of node.js [https://nodejs.org/ here]. The installer will also set the class path and install '''npm''' (the node.js package manager), both of which are necessary for the next steps.
Download our Javascript examples [[#Quick Downloads|here]].
In the terminal, navigate to the folder that contains the Phidgets Javascript examples. There, type the following command:
{{Code|npm update}}
This will cause the package manager to look at {{Code|package.json}} and update the Phidgets libraries.
Follow the README in the Javascript libraries to get the Phidget network server running.
In the terminal, navigate to the folder that contains the Phidgets Javascript examples and type
{{Code|node <example> <address>}}
where {{Code|<example>}} is the filename of the example you want to run (i.e. DigitalInput.js) and {{Code|<address>}} is the address of the Phidget server. In our case, it will be "localhost" because we're hosting it on the same computer:
{{Code|node DigitalInput localhost}}
This should result in a simple text-based example to be launched inside the terminal.


== Edit the Examples ==
== Edit the Examples ==
By following the instructions for your operating system and compiler above, you now have working examples and a project that is configured. This teaching section will help you understand how the examples were written so you can start writing your own code.
{{WriteCode_Intro|JavaScript}}
 
 
Remember: your main reference for writing Objective-C code will be the {{Phidget22API}} Manual and the example code.


=== Step One: Connect===
=== Step One: Connect===
In Javascript, you must first connect to the Phidget server using the {{Code|Connection}} object.
In Javascript, you must first connect to the Phidget server using the {{Code|Connection}} object. Have a look at the Connection API for more details: {{Phidget22API}} -> Select JavaScript then select Connection API.


<syntaxhighlight lang=javascript>
<syntaxhighlight lang=javascript>
function main() {
function main() {
 
    var conn = new phidget22.Connection(5661, 'localhost');
...
    conn.connect().then(function () {
 
        console.log("Connected");
var conn = new jPhidget22.Connection(url, { name: n, passwd: p });
        runCode();
conn.connect()
    }).catch(function (err) {
  .then(runCode);
        console.error("Failed to connect", err);
    });
}
}
</syntaxhighlight>


</syntaxhighlight>
Once a connection has been established, it will stay active until it is closed, even across network outages and server restarts.


Where {{Code|url}}, {{Code|n}}, and {{Code|p}} are variables defined elsewhere in the program. If the connection is successful, we call another function that contains the rest of our code.
Multiple Connections can be created and connected at once. Any opened Phidget or Manager objects  will match against devices on all connections.


=== Step Two: Create and Open===
=== Step Two: Create and Open===
After connecting, the {{Code|Open()}} function opens the software object, and once it has successfully opened we can interact with it and start receiving data from it. We can also set up event handlers just before opening.
After connecting, create a new channel object of the correct channel class, then call the {{Code|open()}} function to open the channel. Once it has successfully opened we can interact with it and start receiving data from it. We can also set up event handlers just before opening.


For example, if we were using an Digital Input as our device, it would look like this:
For example, if we were using an Digital Input as our device, it would look like this:
Line 345: Line 167:


function runCode() {
function runCode() {
var ch = new jPhidget22.DigitalInput();
    var ch = new phidget22.DigitalInput();


ch.onAttach = digitalInput_attach;
    ch.onAttach = digitalInput_attach;
ch.onStateChange = digitalInput_change;
    ch.onStateChange = digitalInput_change;
 
ch.open().then(function() {
// code to execute after open succeeds
}).catch(function (err) {
// code to execute if open fails
});


    ch.open().then(function () {
        // code to execute after open succeeds
    }).catch(function (err) {
        // code to execute if open fails
    });
}
}


</syntaxhighlight>
</syntaxhighlight>


Once the object successfully opens, you can access it and you will start to get events from it. We can define the event handler functions :
Once the channel successfully opens, you can access it and you will start to get events from it. We can define the event handler functions :


<syntaxhighlight lang=javascript>
<syntaxhighlight lang=javascript>


function digitalInput_attach(ch) {
function digitalInput_attach(ch) {
console.log(ch + ' attached');
    console.log(ch + ' attached');
}
}


function digitalInput_change(state) {
function digitalInput_change(state) {
console.log('state changed:' + state);
    console.log('state changed:' + state);
}
}


Line 382: Line 203:


var di_state = ch.getState(); // get the state of the digital input
var di_state = ch.getState(); // get the state of the digital input
ch.setState(1); // set the state of the digital input


</syntaxhighlight>
</syntaxhighlight>


=== Step Four: Close ===
=== Step Four: Close ===
At the end of your program (or at least, at the end of the part that uses the Phidget), it is advisable to close your device. This ensures that the Phidget will be available to other programs that want to use it, since a channel can only be in use by one program at a time unless it's opened remotely. It's not necessary to delete the object after closing in Javascript.
At the end of your program (or at least, at the end of the part that uses the Phidget), it is advisable to close your device. This ensures that the Phidget will be available to other programs that want to use it, since a channel can only be in use by one program at a time unless it's opened via the Phidget Server. It's not necessary to delete the object after closing in Javascript.


<syntaxhighlight lang=javascript>
<syntaxhighlight lang=javascript>

Revision as of 16:18, 9 April 2018

Quick Downloads

Documentation

Libraries

Example Code

Tools

OS Libraries

Getting Started with JavaScript

Welcome to using Phidgets with JavaScript! By using JavaScript, you will have access to the complete Phidget22 API, including events. We also provide example code in JavaScript for all Phidget devices.

Version Change

Note: The Phidgets JavaScript library has been bumped to version 2.x.x following a rewrite. The version 2 API is mostly identical to version 1, but does have some breaking changes. It is highly recommended that any code written against version 1 be updated to version 2, as version 1 is considered unstable.

Phidget Network Server

The JavaScript library requires the Phidget Network Server. Start by configuring the server for your OS:

The Phidget Server includes a built-in Webserver. This must be enabled when using the JavaScript library in browser, but can be left disabled when using the library from Node.js.

The Phidget Server Webserver can be used to serve files - such as the Phidget JavaScript library, or your own projects. By default, it serves the JavaScript control panel files. The main purpose of the Webserver is to support a Websockets connection for the Browser library - because regular sockets cannot be used in Browser. The Node.js library uses raw sockets to connect to the Phidget Server, and so does not require the Webserver or Websockets.

JavaScript Control Panel

The JavaScript control panel is a Browser version of our Phidget control panel. This can be used to view and control all Phidgets attached to a Phidget server. The JavaScript control panel is installed by default on Windows, macOS and PhidgetSBC. You can also download the source here.

Make sure the Phidget Server - Webserver is enabled, and running, then navigate to http://localhost:8989. You will now see a program written with JavaScript/HTML that mimics the Phidget Control Panel. It will show all the Phidgets attached to your machine. By double-clicking on the Phidgets, and example will launch.

Javascript windows controlpanel.png

Browser

Use Our Examples

One of the best ways to start programming with Phidgets is to use our example code as a guide. Our browser examples are available here.

Write Your Own Code

Let's start by writing a simple HTML page that makes a dynamic list of attached Phidgets visible to the user. We will be using the JavaScript library jQuery in these examples. jQuery is not required in order to use Phidgets, however, it will make it easier for us to access elements on an HTML page.

To start, create a new empty folder.

Next, download the latest JavaScript browser library from here and copy the files into the folder.

Next, create a file called index.html and copy the following code into it (Note: if you have a newer jQuery, modify the code below to match your version): 

<!DOCTYPE html>
<html>
<head>
    <title>Phidget Manager</title>
    <script src="jquery-2.1.4.min.js"></script>
    <script src="sha256.min.js"></script>
    <script src="phidget22.min.js"></script>
    <script>
        $(document).ready(function() {
            var conn = new phidget22.Connection(8989, 'localhost');

            conn.connect().then(function() {
                console.log('connected');
            }).catch(function(err) {
                conn.delete();
                alert('failed to connect to server:' + err);
            });

            var man = new phidget22.Manager({
                onDeviceAttach: function(dev) {
                    $('#list').append(new Option(dev.getDeviceName(), dev.getKey()));
                },
                onDeviceDetach: function(dev) {
                    $("#list option[value='" + dev.getKey() + "']").remove();
                }
            });
            man.open();
        });
    </script>
</head>

<body>
    <label> Attached Phidgets: </label>
    <div>
        <select multiple id="list" style="width: 500px; height: 200px"></select>
    </div>
</body>
</html>

This code uses the Phidget Manager to list any Phidget accessible from your computer (either directly via USB or indirectly over the network).

Finally, double click index.html to open it in a browser. You should see something like this:

Javascript windows example.png

Open the developer console to get a better idea what is going on:

Javascript windows devconsole.png

For information about the Node.js examples, keep reading. Otherwise, skip ahead to the edit the examples section located below.

Node.js

Use Our Examples

One of the best ways to start programming with Phidgets is to use our example code as a guide. In order to run the examples, you will need to download and install Node.js.

Now that you have Node.js installed, select an example that will work with your Phidget:

Navigate to the example folder that you previously downloaded, open the command prompt at this location and enter the following command: 

npm update

Javascript windows npmupdate.png

Next, enter the following command to run the example (replacing Accelerometer with your example name): 

node Accelerometer localhost
Javacsript windows nodeexample.png

You should now have the example up and running. When you are ready, the next step is editing the examples.

Edit the Examples

By following the instructions for your operating system and compiler above, you now have working examples and a project that is configured. This teaching section will help you understand how the examples were written so you can start writing your own code.


Remember: your main reference for writing JavaScript code will be the Phidget22 API Manual and the example code.

Step One: Connect

In Javascript, you must first connect to the Phidget server using the Connection object. Have a look at the Connection API for more details: Phidget22 API -> Select JavaScript then select Connection API. 

function main() {
    var conn = new phidget22.Connection(5661, 'localhost');
    conn.connect().then(function () {
        console.log("Connected");
        runCode();
    }).catch(function (err) {
        console.error("Failed to connect", err);
    });
}

Once a connection has been established, it will stay active until it is closed, even across network outages and server restarts.

Multiple Connections can be created and connected at once. Any opened Phidget or Manager objects will match against devices on all connections.

Step Two: Create and Open

After connecting, create a new channel object of the correct channel class, then call the open() function to open the channel. Once it has successfully opened we can interact with it and start receiving data from it. We can also set up event handlers just before opening.

For example, if we were using an Digital Input as our device, it would look like this: 

function runCode() {
    var ch = new phidget22.DigitalInput();

    ch.onAttach = digitalInput_attach;
    ch.onStateChange = digitalInput_change;

    ch.open().then(function () {
        // code to execute after open succeeds
    }).catch(function (err) {
        // code to execute if open fails
    });
}

Once the channel successfully opens, you can access it and you will start to get events from it. We can define the event handler functions : 

function digitalInput_attach(ch) {
    console.log(ch + ' attached');
}

function digitalInput_change(state) {
    console.log('state changed:' + state);
}

Now that they've been registered in the runCode() function and the device has been opened, these event handlers will be able to trigger. The first one triggers when the DigitalInput channel attaches, and the second one will trigger whenever the state of the attached DigitalInput changes.

Step Three: Do Things with the Phidget

Some values can be directly read and set on the Phidget. These functions can be used inside a polling loop as an alternative to event driven programming. The lines inside the loop would be something like this, after which you could do something with the value: 

var di_state = ch.getState(); // get the state of the digital input

Step Four: Close

At the end of your program (or at least, at the end of the part that uses the Phidget), it is advisable to close your device. This ensures that the Phidget will be available to other programs that want to use it, since a channel can only be in use by one program at a time unless it's opened via the Phidget Server. It's not necessary to delete the object after closing in Javascript. 

ch.close();

Further Reading

Phidget Programming Basics - Here you can find the basic concepts to help you get started with making your own programs that use Phidgets.

Data Interval/Change Trigger - Learn about these two properties that control how much data comes in from your sensors.

Using Multiple Phidgets - It can be difficult to figure out how to use more than one Phidget in your program. This page will guide you through the steps.

Polling vs. Events - Your program can gather data in either a polling-driven or event-driven manner. Learn the difference to determine which is best for your application.

Logging, Exceptions, and Errors - Learn about all the tools you can use to debug your program.

Phidget Network Server - Phidgets can be controlled and communicated with over your network- either wirelessly or over ethernet.

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