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    0.2.3 • Public • Published

    Chow Chow | Json Envelope

    Provides json response envelopes to chowchow, similar to api-formatter.


    // An example endpoint
    export async function showProduct({ req, sendData, sendFail }: Context) {
      if (! {
        sendFail([`Please provide an 'id'`])
      } else {
        let product = await findProduct(

    Here's how to configure it:

    import { ChowChow, BaseContext } from '@robb_j/chowchow'
    import {
    } from '@robb_j/chowchow-json-envelope'
    type Context = BaseContext & JsonEnvelopeConfig
    // App entry point
    ;(async () => {
      let chow = ChowChow.create<Context>()
      // Add the module
      chow.use(new JsonEnvelopeModule({ handleErrors: true }))
      // Adds new methods to the context
      chow.applyRoutes((app, r) => {
        app.get('/', r(ctx => ctx.sendData({ msg: 'Hey!' })))
        app.get('/err', r(ctx => ctx.sendFail(['Something broke :S']), 418))
      // Run chow
      await chow.start()


    • Adds a sendData & sendFail method to the context to send formatted responses
    • Defaults name & version in the envelope from package.json values
      • Configure this by passing them to the constructor
    • Optionally handle express errors by passing handleErrors
      • Any errors thrown from routes will be formatted in the envelope
      • See Catching errors for more

    Success Response, HTTP 200

      "meta": {
        "success": true,
        "messages": [],
        "name": "my-fancy-api",
        "version": "v1"
      "data": {
        "msg": "Hey!"

    Failure Response, HTTP 400

      "meta": {
        "success": false,
        "messages": ["Something broke :S"],
        "name": "my-fancy-api",
        "version": "v1"
      "data": null

    Catching errors

    You can pass handleErrors to add a chowchow error handler which will catch errors and send the error message to sendFail.

    The error handler will look at what was throw to determine how to send back an error.

    • It will see if the object is an iterator, looking for Symbol.iterator.
    • It will look for a string directly
    • It will use an Error's message

    Dev Commands

    # Lint the source code
    npm run lint
    # Manually format code
    # -> This repo runs prettier on git-stage, so committed code is always formatted
    npm run prettier
    # Run the unit tests
    npm test
    # Generate code coverage in coverage/
    npm run coverage


    npm i @robb_j/chowchow-json-envelope

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    • robb_j