JSON Overview

JSON Overview

  "location": {
    "name": "Los Angeles",
    "country": "USA",
    "region": "California",
    "lat": "34.018",
    "lon": "-118.284",
  "current": {
    "observation_time": "01:56 AM",
    "temperature": 63,
    "weather_descriptions": [
      "Partly cloudy"
    "humidity": 56,


  • We want our device to interact with services all over the internet–e.g. permanently store all heart rate data in the cloud, retrieve the weather forecast tomorrow, etc.
  • APIs provide the mechanism we use to communicate with these other services
  • Webhooks are created in the Particle cloud to connect our Argon to an API online

Examples of APIs

Review: Process to Interacting with Data from API

  • Identify API you want to use (make account if necessary)
  • Create a Particle webhook that interacts with the API
  • Use Particle.publish to trigger webhook (review)
  • Use Particle.subscribe to “listen” for response from webhook (optional)
  • Create function handler that is used by Particle.subscribe to process JSON

Where does JSON come in?

  • Sending one temperature value to a webservice is not hard
  • Sending dozens of sensor every second requires creating much more complex way of representing / store those values so we can send them to the cloud
  • JSON is an excellent, common way we exchange complex data

JSON (JavaScript Object Notation)

  • Popular format for exchanging data with web services
    • XML is another
  • JSON is useful because we can represent complex data with a simple string, and then share that data between two different services
  • JSON is not a programming language; it is a way of representing complex data as a string
  • Typically, programmers use library to read (parse) and write JSON

JSON Overview

  • JSON is a way of representing an object as a text string
  • Built around key-value pair idea (like a dictionary or hash)
  • Two data types
    • objects (single item denoted with { })
    • arrays (multiple items denoted with [ ])

JSON Basics - Objects

{ "weather": "sunny", 
  "temp": 78.000, 
  "humidity": 32 
  • Inside { } is the JSON object
  • Keys are to the left of the : and are always strings
  • Values are to the right of the : and can be string, int, float, objects, or arrays
    • Ex:"weather" is a key and "sunny" is its value
    • Ex: "sunny" is a string, 78.000 is a double or float, 32 is an int

JSON Basics - Nested Objects

      "forecast": {
        "mon": {
          "high": 89,
  • Values can be JSON objects
    • Ex: forecast is a key and the value is "mon"
    • "mon" is itself a key which store the keys "high" and low

JSON Basics - Arrays

{ "daily_temp": [
  • Arrays are specified with [ ]
  • Indices begin at 0 and up to length - 1
  • Elements of arrays can be string, int, float, objects, or arrays
    • Ex:"daily_temp" is a key and its value is an array
    • Ex: 89 is an int and is at index0