node.js routes validate json body - json

Question

Im using express, body-parser and moongose to build a RESTful web service with Node.js. Im getting json data in the body of a POST request, that function looks like this:
router.route('/match')
// create a match (accessed at POST http://localhost:3000/api/match)
.post(function(req, res) {
if (req._body == true && req.is('application/json') == 'application/json' ) {
var match = new Match(); // create a new instance of the match model
match.name = req.body.name; // set the match name and so on...
match.host = req.body.host;
match.clients = req.body.clients;
match.status = req.body.status;
// save the match and check for errors
match.save(function(err) {
if (err) {
//res.send(err);
res.json({ status: 'ERROR' });
} else {
res.json({ status: 'OK', Match_ID: match._id });
}
});
} else {
res.json({ status: 'ERROR', msg: 'not application/json type'});
}
});
The model Im using for storing a match in the database looks like this:
// app/models/match.js
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var MatchSchema = new Schema({
name: String,
host: String,
clients: { type: [String]},
date: { type: Date, default: Date.now },
status: { type: String, default: 'started' }
});
module.exports = mongoose.model('Match', MatchSchema);
But how do I validate that the json data in the body of the POST request has the key/value fields I want? For clarification, I dont want to insert data in the database that is incomplete. If I test to skip a key/value pair in the json data I get a missing field in the database and when I tries to read req.body.MISSING_FIELD parameter in my code I get undefined. All fields except date in the model is required.
Im using json strings like this to add matches in the database
{"name": "SOCCER", "host": "HOST_ID1", "clients": ["CLIENT_ID1", "CLIENT_ID2"], "status": "started"}

Answer 1

I use a very simple function that takes an array of keys, then loops through it and ensures that req.body[key] is not a falsy value. It is trivial to modify it to accommodate only undefined values however.
In app.js
app.use( (req, res, next ) => {
req.require = ( keys = [] ) => {
keys.forEach( key => {
// NOTE: This will throw an error for ALL falsy values.
// if this is not the desired outcome, use
// if( typeof req.body[key] === "undefined" )
if( !req.body[key] )
throw new Error( "Missing required fields" );
})
}
})
in your route handler
try{
// Immediately throws an error if the provided keys are not in req.body
req.require( [ "requiredKey1", "requiredKey2" ] );
// Other code, typically async/await for simplicity
} catch( e ){
//Handle errors, or
next( e ); // Use the error-handling middleware defined in app.js
}
This only checks to ensure that the body contains the specified keys. IT won't validate the data sent in any meaningful way. This is fine for my use case because if the data is totally borked then I'll just handle the error in the catch block and throw an HTTP error code back at the client. (consider sending a meaningful payload as well)
If you want to validate the data in a more sophisticated way, (like, say, ensuring that an email is the correct format, etc) you might want to look into a validation middle-ware, like https://express-validator.github.io/docs/