Pragmatic tools to build JSON api endpoints.

Usage no npm install needed!

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  import expressApiTools from '';



A few simple and pragmatic tools to quickly build API endpoints based on Express.

Basic api modules

This package contains a few modules which can be useful for quickly building JSON api's. The most notably is the register_endpoint, which leverages caching and rate limiting using Express as server.


Simple logging, used by the other modules but can be used on its own too.

const log = require('express-api-tools').logging;

Logging can be enabled or disabled:


Or it can be enabled based on a given startup parameter:


Starting the app using the following command will then enable logging:

node app.js log

Messages can be logged:'some message');
log.error('some error');

Currently there is no difference between info and error logging, this might be included in a future version.


Simple caching mechanism to cache API responses. It is used by the register_endpoint module, but can be used on its own.

const cache = require('express-api-tools').cache;

Quick example:

const cachedResponse = cache.getFromCache('get', req.originalUrl); // Where originalUrl is the cache key

if (cachedResponse) {
    res.end(cachedResponse); // Respond to client with cached response
} else {
    // Do some stuff to obtain jsonResult
    res.end(jsonResult); // Respond to client with jsonResult
    cache.putInCache('get', req.originalUrl, 1000, jsonResult); // Cache the jsonResult for 1 second
    cache.cleanupCache(); // Cleanup out dated cache entries

Register Endpoint

Pragmatic approach to register endpoints on Express that can be cached and (if required) rate limited.

Without rate limiting:

const express = require('express'),
    app = express(),
    registerEndpoint = require('express-api-tools').register_endpoint.default, // Default is without rate limiting
    cacheTime = 60000; // Cache for 1 minute

registerEndpoint(app, '/api/some-endpoint', cacheTime, implementation); // Where implementation is a method that returns the api response

When a client requests the /api/some-endpoint resource, the implementation is called. It will not be called again for the next minute.

With rate limiting:

const express = require('express'),
    app = express(),
    registerEndpoint = require('express-api-tools').register_endpoint,
    cacheTime = 60000; // Cache for 1 minute
registerEndpoint.withRateLimit(app, '/api/some-endpoint/:variable', cacheTime, implementation, 1000);

function implementation({variable}) {
    // Do something with the variable

The implementation will not be called more often than once a second (1000ms). If the implementation was successfully called, it will be cached for 1 minute (60000ms).

It is possible to use variables in the api request pretty easily.

JSON Fetch

Another pragmatic utility to call other api endpoints that will respond with json. This utility supports mocking that data using mockfiles.


const jsonFetch = require('express-api-tools').jsonFetch;

jsonFetch.getJson('', headers).then(body => {
    // Do something with json body
}).catch((err) => {
    const {error, response} = err;
    if (response) {
        // There was a response with  status code other than 200
        // The error variable contains the error message
        response.json().then(body => {
            // Json body could be parsed
        }).catch(() => {
            // The response body was not in json
    } else {
        // Something else went wrong, the err variable contains the error

A simple post variant is also available.


Mocks can be enabled by starting the server using a command line argument: mocks=./someMocksFile.json. The mocks file contains a simple json object with key/values. The key is the exact url that is fetched by jsonFetch, the value is a reference to another json file which contains the response that should be returned. If the value is 'ENOTFOUND', a not found error will be simulated.

    "": "./mocks/google_mock.json",
    "": "ENOTFOUND"

It is possible to enable logging of all calls that are not mocked while mocks are enabled. This can be used to trace unmocked calls, if needed. This can be done by adding the command line argument: report-unmocked=true.

Mock recording

Mocks can also automatically be recorded (to take a snapshot of a specific moment). Add the following command line argument: generate-mocks=./some/path/someMocksFile.json. The mocks file will be appended if it already exists. Otherwise, it will be created and all recorded mocks will be automatically added. The actual responses will be recorded in separate json files that will be saved in the same directory as the specified mocks file. If a response is recorded once, subsequent calls to the same endpoint will return the mocked response.

Api endpoints

This package also contains a few example api endpoints that can be used in production.


Simple endpoint that can provide information about the environment on which the server runs. Can be useful in situations where dev, test, acc and prod environments are separated. The environment name (string) must be placed in a system variable on the system where the node server is running. This module will provide the contents of that system variable to the frontend, it will default on a specified value if no system variable is set.

When requiring it, it takes two arguments, the system variable to read and the default value to use when no system variable is set.


const express = require('express'),
    app = express(),
    env = require('express-api-tools').env('NODE_ENV', 'prod');

env.api(app, '/api/env');


A very basic health indicator that just returns 200. Can be used in environments where this api server is monitored to be available.


const express = require('express'),
    app = express(),
    health = require('express-api-tools').health;

health.api(app, '/api/health');


Api endpoint that will return the uptime of the server since the node process was started OR since it was last reset. The reset can be useful to remotely reset the uptime. If it is paired with a mechanism on the frontend that will refresh the page when the uptime is lower than the last retrieved uptime value, it can be used to make all connected frontends perform a refresh. This might be useful when this service serves a dashboard or monitoring application.


const express = require('express'),
    app = express(),
    uptime = require('express-api-tools').uptime;

uptime.api(app, '/api/uptime');