mosh.js

A simple null / empty checker

mosh.js is a simple tool for null or undefined or falsey value checks in node.js apps. It provides a neat abstraction for if-else blocks and relieves the developer of the headaches that come with logic-fuzz.

How to use

Intall using npm sudo npm install mosh

Require mosh in your code and init as a middleware before your route definitions

var mosh = require('mosh'),
    express  = require('express');
app.set('view engine', 'ejs');
app.set('views', './public/views');
var app = new express();
//Init mosh
app.use(mosh.initMosh);

//Example route using mosh checks
app.get('/', function (req, res, next) {
    res.mosh.emptyCheck(req.query.access_token, 'Access token needed to view this page');
    res.mosh.callE('render','index', {user:'mosh',page:'Index'});
});

//Init mosh's error handler
app.use(mosh.initMoshErrorHandler);

One caveat with using mosh. Unlike php where we can easily use die() / exit() to stop code execution. Node.js has no 'easily' implementable equivalent functions. calling res.render or any other response.end / response header change invoking functions after mosh causes a 'header already sent' error. mosh handles this by using the mosh.callE wrapper for such functions described above. The only thing you need to do is include the function name as the first argument to mosh's callE function and subsequent ones as you would normally (and in the same order) pass to the function. So, res.render('ejsfilename',ejstemplatepayload) becomes res.mosh.callE('render','ejsfilename',ejstemplatepayload) AND res.json({random:1234}) becomes res.mosh.callE('json',{random:1234})

Example Use-case 1

Typical flow

var secure = req.param('secure');
if (!secure) {
    res.forbidden('This request has to be secure!');
}else{
  //other stuff here
}

mosh flow

var secure = req.param('secure');
res.mosh.emptyCheck(secure, 'This request has to be secure', 'forbidden');
//If secure is empty, code won't go beyond the mosh.emptyCheck call
// other stuff here

Example Use-case 2

Typical flow

var client_id     = req.query.client_id;
var client_secret = req.query.client_secret;
//imagine we have more required (query) params 
if(!client_id || !client_secret){
   res.fail('client_id and client_Secret are required');
}
//other app stuff

mosh flow

res.mosh.multiArrayCheck(req.query, ['client_id','client_secret']); 
//Code won't go beyond the mosh.multiArrayCheck call if any of the passed values fail.
var client_id     = req.query.client_id;
var client_secret = req.query.client_secret;

Example Use-case 3

Typical flow

var user_id = req.params.user_id;
if(!user_id)
{
	res.fail('User  id is required');	
}
else
{
	
	UserModel.findOne(user_id, function(user, err){
		if(!user){
		   res.fail('User not found');
		}
		else
		{
			//other stuff to happen if user is found
	    }
	});

}

mosh flow

res.mosh.emptyCheck(req.params.user_id, 'User id is required', 'fail');
var user_id = req.params.user_id;
UserModel.findOne(user_id, function(user, err){
	res.mosh.emptyCheck(user, 'User not found', 'fail');
	//other stuff to happen here
});

Example Use-case 4

Typical flow

if(req.body.IGUser && req.body.IGuser.handle){
	var IGUserHandle = req.body.IGUser.handle;
}
else{
	res.fail('Required handle property not found in USER');
}

mosh flow

res.mosh.multiDepthCheck(req.body, ['IGuser', 'handle'],'Required handle property not found in USER');
var IGUserHandle = req.body.IGUser.handle

Use Mosh outside of express

var Mosh = require('mosh');
var mosh = new Mosh(null); //Don't pass a res object

mosh.emptyCheck(false, 'You shall not pass'); //Throws an error with the message you shall not pass.
mosh.multiArrayCheck({'name':'Lawal',token:'0399940'}, ['client_id','client_secret']);  //Throws an error