api-mid-mock

The api mock middleware that allows to serve local files as responses to intercepted api calls. Ideally feats to webpack-dev-server like Angular proxy server.

features

🔥 Built in support for hot mocks replacement
🚀 Quickly and easily configure the API via JSON
📂 Or using the mock files structure

Installation

npm install api-mid-mock --save-dev

Bypass function

Call APIMocker() function to get the pre-configured bypass function.

There is object with four parameters, that you can pass to:

• path - specifies path to config file or all mocks root folder, by default ./mocks
• useFiles - boolean flag that allows adding the mock files to configuration, by default false
• acceptOnlyJSON - boolean flag to skip loading route from browser application by checking Accept header, by default true
• watch - boolean flag to disable the fs.watch that implements the hot mocks replacement (can be helpful on systems where fs.watch is broken), by default true

Files based usage

Put your JSON files in folder, for example ./mocks:

./mocks
    /api
        /users.json
        /goods.json

And add proxy configuration proxy.config.js (for Angular application):

const APIMocker = require('api-mid-mock')

module.exports = [{
    context: () => true,
    target: 'https://your.domain',
    bypass: APIMocker({path: './mocks', useFiles: true}),
}]

Or put it into devServer.proxy section into your webpack config.

That's it!

When you'll perform requests to /api/users or /api/goods, the proxy server will intercept it and return JSON from existed files. All other requests will be passed to your back-end.

To distinguish different HTTP methods, just call the files with according prefix:

./mocks/api
    /get.users.json
    /post.users.json

Config based usage

The same as previous, but put to ./mocks folder the index.js file, that returns an object describes the configuration:

module.exports = {
    'get /api/users': require('./api/get.users.json'),
    'post /api/users': require('./api/post.users.json'),
    '/api/goods': [
        {id: 1, price: 100.00, title: 'Sample'},
        {id: 2, price: 99.99, title: 'Worse'}
    ],
    '/api/goods/:id': function(req, res) {
        const {id} = req.params
        if (id === '1' || id === '2') {
            res.end(JSON.stringify({status: 'Found!'}))
        } else {
            res.statusCode = 400
            res.end('Bad Request')
        }
    }
}

The key string format

method /path/:param/*?query=value

Method

The method is case-insensitive. It can be one of HTTP methods like GET or POST. Or it can be ANY or * or just omit it to match with any request methods.

Path

The path describes the part or URL that can contain wildcards and parameters.

Wildcard * in a path matches any substring.

Params allows you to deal with dynamics URLs and you can get an according value from the req.params.

Query params

It is possible to filter requests by query parameters. You can use only parameter name to check if it exists: ?param. Or check full coincidence for a name and value: ?param=value.

Responses

There are three types of responses: strings, objects and function.

The strings will be returned as is.

The objects will be translated to string by JSON.stringify and returned with the Content-type: application/json header.

The functions

The functions can fully manage the request and response with according parameters.

If you need to pass the request to back-end just return null or undefined from the function.

But there is one difference with webpack-dev-server bypass function. You cannot return the path to the file to return it as response. Please, use require or other ways to get the response content and return the content.

To end the request without body, return true from function.

Chokidar usage

Because of fs.watch is broken on some systems, you can use chokidar to watch files changes.

Here is the example how to wrap APIMocker with chokidar in webpack.config.js:

let mocker = () => {}
chokidar.watch('./mocks').on('all', () => {
    mocker = APIMocker({path: './mocks', watch: false})
})

module.exports = [{
    context: () => true,
    target: 'https://your.domain',
    bypass: (req, res, next) => mocker(req, res, next),
}]

Node.js example

You can run server with mock data without webpack, with node.js only.

Here is the example of server.js file:

const http = require('http')
const url = require('url')
const APIMock = require('api-mid-mock')

const mocked = APIMock({ path: './index.js', acceptOnlyJSON: false })

const requestListener = function (req, res) {
    req.accepts = () => req.headers.accept?.split(',').map((s) => s.replace(/;.+$/, '')) || []
    const parsedUrl = url.parse(req.url, true)
    req.path = parsedUrl.path.replace(parsedUrl.search, '')
    req.query = parsedUrl.query
    req.params = {}

    mocked(req, res, () => {}).then((result) => {
        if (!result) {
            res.writeHead(400)
            res.end('Please, try supported requests')
        }
    })
}

const server = http.createServer(requestListener)
server.listen(80)

To start the server just run node server.js.

The small helper to get the request body:

function body(req) {
    return new Promise((resolve) => {
        let body = ''
        req.on('data', (chunk) => {
            body += chunk.toString()
        })
        req.on('end', () => {
            try {
                body = JSON.parse(body)
            } catch {}
            resolve(body)
        })
    })
}

use it with await:

const data = await body(req)