Schema

Validates JSON data received over HTTP using typed schemas. This is a typical use case: data arrives from an external API as unknown, and you need to verify its shape before using it. See the schema API reference for caveats, when to use, and the full type surface.

Hardware

Any ESP32 board with WiFi
USB cable

Code

import * as s
 from 'mikro/schema'

// Define a schema for the API response
const WeatherResponse
 = s
.object
({
  temperature
: s
.number
(),
  humidity
: s
.number
(),
  description
: s
.optional
(s
.string
()),
})

// Simulate data arriving from an HTTP API
const raw
: unknown = JSON
.parse
('{"temperature": 22.5, "humidity": 45.2}')

const result
 = s
.parse
(WeatherResponse
, raw
)
if (result
.ok
) {
  console
.log
(`Temperature: ${result
.value
.temperature
}`)
  console
.log
(`Humidity: ${result
.value
.humidity
}`)
} else {
  console
.error
('Invalid response:', result
.error
)
}

Walkthrough

Define a schema. s.object({...}) describes the expected shape. Each field gets a type validator like s.number() or s.string().
Parse untrusted data. s.parse() checks the data against the schema and returns a Result. On success, result.value is fully typed. On failure, result.error tells you what went wrong and where.
No exceptions. Validation never throws. You always get a Result to handle both cases explicitly.

Create project

pnpmnpmyarnbun

pnpm create mikro --template schema

npm create mikro -- --template schema

yarn create mikro --template schema

bun create mikro --template schema

Run it

pnpmnpmyarnbun

pnpm install
pnpm mikro flash  # only needed once per board
pnpm mikro dev

npm install
npx mikro flash  # only needed once per board
npx mikro dev

yarn install
yarn mikro flash  # only needed once per board
yarn mikro dev

bun install
bunx mikro flash  # only needed once per board
bunx mikro dev

The console prints the valid readings and commands, and clear error messages for the invalid ones.

View source on GitHub

Schema ​

Hardware ​

Code ​

Walkthrough ​