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The main feature of this library is the getMiddlewareVersion function which facilitates passing variables between middlewares seamlessly. A great feature of this library is that it allows its users to create their own handlers for passing variables.


var express = require('express');
var ExpressPlus = require('expressjs-plus').ExpressPlus;
var app = express();
// simple handler example
var userHandler = function (param, paramsArray, req, res) {
    if (param !== 'user') return false;
    paramsArray.push("USER WAS FOUND!");
    return true;
// this handler allows you to pass res.locals properties between your middlewares seemingly,
// it the parameter was found in locals, it attaches it to paramsArray.
var resLocalsHandler = function (param, paramsArray, req, res) {
    if (param in res.locals) {
        return true;
    } else return false;
var appPlus = new ExpressPlus(app, [userHandler, resLocalsHandler], []);
var regularFunction = function (user, id, cb) {
    return cb(null, {response: {user: user, id: id}, status: 200, resLocalsVar: "passVar"});
// resLocalsVar was passed in a previous method
var regularFunction2 = function (resLocalsVar, user, id, cb) {
    // now you can have access to it
    return cb(null);
// the responder at the end will use res.locals.status and res.locals.response to issue an HTTP response
app.use(appPlus.GMV(regularFunction), appPlus.GMV(regularFunction2), appPlus.responder);
// adds error handlers, it will add a default error handler along with the list of error handlers passed
// in this case, no error handlers were passed
app.listen(3001, function () {

Another example for a paramHandler

function userHandler(param, paramsArray, req){
    if(param === 'user'){
        return true;
        return false;


npm install expressjs-plus


Kind: global class

new exports.ExpressPlus(app, passedParamHandlers, passedErrorHandlers)

This function abstracts the constraints of express middleware signature and allows you to easily pass variables between middlewares without ugly code. It introduces a neat pattern for passing these variables.

Param Type Description
app Object express app object
passedParamHandlers Array array of functions in the format of @see lastHandler
passedErrorHandlers Array array of middlewares


Kind: instance class of ExpressPlus

new this.HTTPError(status, errCode)

Generic error handler

Param Type Description
status Number HTTP error code
errCode String errorCode, the error handler should handle this

expressPlus.getMiddlewareVersion ⇒

Returns a middleware version of the function passed, this function replaces the last parameter with a callback function to work with express js.

Kind: instance property of ExpressPlus
Returns: function

Param Type Description
func function the function to be converted


function regularFunc(someVar, cb){
    return cb(null, {response: someVar+="addedString"});
// middleware version of regularFunc
var func = GMV(regularFunc);
// func will behave like this
function mw(req, res, next){
    let someVar = req.query.someVar;
    res.locals.response = someVar+="addedString";
    return next();

expressPlus.getMiddlewareVersionPromise ⇒

Similar to GMV @see GMV but accepts promises instead

Kind: instance property of ExpressPlus
Returns: function

Param Type Description
promise Promise the promise to be converted


function regularPromise = (someVar) => {
// you can use co as well
    return new Promise((resolve, reject) => {
        resolve({ response: {user: user, id: id}, status: 123 });
// middleware version of regularFunc
var func = GMVPromise(regularFunc);


sets error handlers, make sure to use this last

Kind: instance method of ExpressPlus

expressPlus.responder(req, res, next)

Handles responses. Other middlewares need to use locals to pass data to this function

Kind: instance method of ExpressPlus

Param Type Description
req Object request object
res Object response object
res.status function function to set the status
res.locals Object object that is used to pass data around
res.locals.status Number Contains HTTP status code
res.locals.response Object Contains the response body
next function

expressPlus.defaultCbWithResponse(cb, [status])

Handles callbacks and puts response & status in the second callback argument if successful Replace your callback with this if appropriate.

Kind: instance method of ExpressPlus

Param Type Default Description
cb function callback function
[status] Number 204 optional argument to pass specific HTTP code if no errors were found if the status is 204, no response will be returns according to HTTP codes.

expressPlus.defaultCb(cb, [resource])

Handles callbacks. Replace your callback with this if appropriate.

Kind: instance method of ExpressPlus

Param Type Description
cb function callback function
[resource] Object optional argument to return instead of the actual result


Enables sending array of middlewares to app.use

Kind: instance method of ExpressPlus


ExpressPlus~lastHandler(param, paramsArray, req, res) ⇒ boolean

Default parameter handler used in getMiddlewareVersion. Every parameter is passed to a set of functions to be handled, this is the last handler that just pushes the parameter to the paramsArray.

Kind: inner method of ExpressPlus
Returns: boolean - if true is returned, the parameter will be considered handled and the function GMV will move on to the next parameter. if false is returned, the next handler on the list will attempt to handle the parameter until this methods turn comes, which will always return true
See: dataHandler this function is a more real example of a parameter handler, it is used to integrate with another library

Param Type Description
param String string parameter
paramsArray Array parameter arrays which will be sent to the underlying function of the middleware
req Object express request object that is used in middlewares, useful for accessing req.params, req.query, etc
res Object exppress response object that is used in middlewares, could be useful if you want to access res.locals


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