Trolley NPM | npm.io

🚋 Trolley

Trolley is an opinionated, easy to use and extensible logging tool and response abstraction for Express-based APIs.

Usage / public API

In action:

// server.js

const Trolley = require('./my-trolley-instance.js');
const { somethingIsWrongWith, allIsGoodWith } = require('./somefile.js');

app.use('/health', (req, res) => Trolley.deliver('API is up and running!', res))

app.use('/myRoute', (req, res) => {
    try {
        if (somethingIsWrongWith(req.data)) {
            Trolley.crash('SomeValue is invalid!', res);
        } else if (allIsGoodWith(req.data)) {
            Trolley.deliver({ updated: true }, res);
        } else {
            Trolley.send({ code: 420, message: 'Hello world!' }, res);
        }
    } catch (e) {
        Trolley.explode({ message: 'Sorry! We\'re experiencing issues.' }, res);
    }
})

Trolley.create({ config })

Trolley.create is the main method used to create a trolley instance. The resulting instance has methods for flusing responses (.deliver, .crash, .explode, .send) as well as methods for adding additional handlers (.onDeliver, etc.)

// my-trolley-instance.js

const trolley = require('trolley');
const { reportBadRequestSomehow, reportExceptionSomehow } = require('./somefile.js')

module.exports = trolley.create({
    onCrash: reportBadRequestSomehow,
    onExplode: reportExceptionSomehow
});

Responses from .crash and .explode both include some metadata about the failed request, to assist with debugging. Given the above .crash usage, the client will receive JSON like this:

{
    "timestamp": 1000000000,
    "status": 400,
    "statusText": "Bad Request",
    "error": "SomeValue is invalid!"
}

Use .crash to return an error-type response, 400 by default. you can provide whatever response code you wish by giving { code: number } or { status: number } or { statusCode: number } within the payload.

Trolley also offers means to set default response handlers in your Express API. For instance, if you always perform some action when a request fails for client-side reasons (4XX errors), or for server-side reasons (5XX errors), you can set those up in just one place.

const trolley = require('trolley').create({
    // onRespond is called for all responses through Trolley
    onRespond: (payload) => console.log('server responded with this payload:', payload),
    // onDeliver is called when .deliver is used (successes)
    onDeliver: (payload) => console.log('huzzah, successful response:', payload)
    // onCrash is called when .crash is used (errors)
    onCrash: (payload) => console.log('server got a bad request', payload),
    // onExplode is called when .explode is used (exceptions)
    onExplode: (payload) => console.log('server ran into an exception!', payload)
});

Trolley.createLogger({ loggerConfig })

Returns a logger, which is a function that takes a single line to log to the output file specified in the loggerConfig.

// logger.js

const trolley = require('trolley');
const logger = trolley.createLogger({
    logPath: 'auth_server.log',
    useLineBreaks: true
})

Trolley.withLogger({ combinedLoggerAndTrolleyConfig })

Returns a trolley instance with a pre-built logger added as an onRespond handler.

Internals / utilities

Trolley.statuses

Map of status codes -> status names, like:

{
  100: 'Continue',
  101: 'Switching Protocols',
  102: 'Processing',
  200: 'OK',
  201: 'Created',
  202: 'Accepted',
  [etc]

Trolley.statusCodes

Map of status names -> status codes, like:

{
  Continue: 100,
  SwitchingProtocols: 101,
  Processing: 102,
  OK: 200,
  Created: 201,
  Accepted: 202,
  [etc]

Trolley.utils

toFunctionArray(whatever)

If given an array of functions, returns that function array. If given a function, returns an array of just that function. If given anything else, returns empty array.

toFunctionArray(null)
=> []

toFunctionArray(myCoolFunction)
=> [myCoolFunction]

toFunctionArray([someFunc, anotherFunc, thirdFunc])
=> [someFunc, anotherFunc, thirdFunc]

stringify(whatever)

Does JSON.stringify, but unwraps the added quotes if the value is already a string.

stringify({ ok: 1234, what: true })
=> '{ "ok": 1234, "what": true }'

stringify(43)
=> '43'

stringify('hey')
=> 'hey'

capitalize(string)

Capitalizes the first letter of the string given. Leaves the rest of the casings untouched.

capitalize('hello there')
=> 'Hello there'

lowercase(string)

Lowercases the whole darn string.

lowercase('OMG!')
=> 'omg!'

camelCase(string)

Splits the string into words (breaking by non-alphanumeric chars), doesn't touch the first word, and runs capitalize on the subsequent words, joining them without spaces.

Warning! This and other code-casing functions remove all whitespace and non-alphanumeric characters.

camelCase('what the heck!? I am only 29.')
=> 'whatTheHeckIAmOnly29'

camelCase('OMG')
=> 'OMG'

camelCase('What is it anyway') // note the capital initial
=> 'WhatIsItAnyway'

camelCase('$)!$(#')
=> ''

pascalCase(string)

Splits the string into words (breaking by non-alphanumeric chars) and runs capitalize on each word, joining them without spaces.

Warning! This and other code-casing functions remove all whitespace and non-alphanumeric characters.

pascalCase('possible unreality')
=> 'PossibleUnreality'

snakeCase(string)

Splits the string into words (breaking by non-alphanumeric chars) and runs lowercase on all of them, joining them by underscores (_).

Warning! This and other code-casing functions remove all whitespace and non-alphanumeric characters.

snakeCase('Possible Unreality')
=> 'possible_unreality'

kebabCase(string)

Splits the string into words (breaking by non-alphanumeric chars) and runs lowercase on all of them, joining them by dashes (-).

Warning! This and other code-casing functions remove all whitespace and non-alphanumeric characters.

kebabCase('Possible Unreality Detected!')
=> 'possible-unreality-detected'

keys(object)

Returns all the keys of an object, same as Object.keys (but with an object-type-check included).

keys('lol')
=> TypeError: 'lol' is not an object.

keys({ ok: 'yes', what: true })
=> ['ok', 'what']

withoutKeys(object, keysToRemove: String[])

Returns the given object without any properties whose names match strings in keysToRemove.

getPayloadStatusCode(payload, defaultCode)

Checks payload for code, status, or statusCode properties containing a number. Returns the first it finds. If none, return defaultCode, or if none given, return 200 if the payload is truthy or 0, otherwise 204 (No Content).