Reading Variables in JavaScript (browser)

In this section we will use in browser JavaScript with jQuery to learn how to read variables from our Spark Cores.

Documentation

As promised earlier each section will start with a documentation section. These sections are no different.

We will be accessing data from our Spark Cores using the Spark Cloud API. The Spark Cloud is a REST API which is extremely easy to use.

• http://docs.spark.io/api/

Also if you need help making requests from jQuery the relevant documentation for $.get (the jQuery method we’ll be using to retrieve data from the Spark Cloud) can be found at:

• https://api.jquery.com/jQuery.get/

List Devices

To list devices make a request to https://api.spark.io/v1/devices and provide your access token as a GET variable.

$.get('https://api.spark.io/v1/devices', { access_token: ACCESS_TOKEN })
  .then(function(res) {
    for (var i in res) {
      var device = res[i];
      console.log(device.name);
    }
  });

Here is an example response from this request

[
  {
    "id": "53ff6f0650723",
    "name": "plumber_laser",
    "last_app": null,
    "last_heard": null,
    "connected": false
  }
]

List Variables

You can also list the variables you have exposed on your Spark. The URL for this query is https://api.spark.io/v1/devices/{DEVICE_ID}. Below is some sample code making this request

$.get('https://api.spark.io/v1/devices/' + DEVICE_ID, { access_token: ACCESS_TOKEN })
  .then(function(res) {
    console.log(res);
  });

{
  id: "54ff6f066678554927290168",
  name: "test",
  connected: true,
  variables: {
    "my_var": "int32"
  },
  functions: [
    "digitalread",
    "digitalwrite",
    "analogread",
    "analogwrite"
  ],
  cc3000_patch_version: "1.29",
  last_heard: "2015-04-30T03:00:26.870Z"
}

Get Variable’s Value

To actually get the value of a variable you make a request to https://api.spark.io/v1/devices/{DEVICE_ID}/{VARIABLE_NAME}. As you probably expect by now example code is below

$.get('https://api.spark.io/v1/devices/' + DEVICE_ID + '/' + VARIABLE_NAME, { access_token: ACCESS_TOKEN })
  .then(function(res) {
    console.log(res.name, res.result);
  });

And of course an example response from the above code:

{
  cmd: "VarReturn",
  name: "test",
  result: 42,
  coreInfo: {
    last_app: "",
    last_heard: "2015-04-30T03:03:06.718Z",
    connected: true,
    last_handshake_at: "2015-04-30T03:02:34.107Z",
    deviceID: "54ff6f066678574927290167"
  }
}

Time To Hook Up A Sensor

Now that we can read variables from our Spark Core it’s time to make those variables interesting by hooking up a sensor.