NodeJS API GET by Id. How to detect item not found? - node.js

Question

I'm developing a GET endpoint to fetch elements from a database(dynamoDB). I'm using Swagger to define the data model in my api. This is the operationId method in my controller:
getInvoiceConfigById: function(req, res) {
var myId = req.swagger.params.id.value;
// InvoiceConfig is a dynamoDb model
// providerId attribute is the unique key of the db table
InvoiceConfig.scan('providerId')
.eq(myId)
.exec(function (err, config) {
if (err) {
console.log("Scan InvoiceConfig error");
throw err;
}
res.status(200).send(config);
});
}
I would like to send a 404 message if the id was not found.
I've noticed in swagger-ui that the body of the response comes empty
Response Body
[]
when the id is not found in the db.
How can I detect in my code when id was not found? I've tried to check if the body of the response is empty:
if(!(config.body))
but this doesn't work because the body is not null

Answer 1

You can check the count of config at server side, if config count is 0 the send desire response code 404 else return 200 response code with data as shown below
getInvoiceConfigById: function(req, res) {
var myId = req.swagger.params.id.value;
// InvoiceConfig is a dynamoDb model
// providerId attribute is the unique key of the db table
InvoiceConfig.scan('providerId')
.eq(myId)
.exec(function (err, config) {
if (err) {
console.log("Scan InvoiceConfig error");
throw err;
}
if (config.length == 0){
res.status(404).end();
} else {
res.status(200).send(config);
}
});
}

Answer 2

Try adding a length check in your callback, like so:
getInvoiceConfigById: function(req, res) {
var myId = req.swagger.params.id.value;
// InvoiceConfig is a dynamoDb model
// providerId attribute is the unique key of the db table
InvoiceConfig.scan('providerId')
.eq(myId)
.exec(function (err, config) {
if (err) {
console.log("Scan InvoiceConfig error");
throw err;
}
if(typeof config === 'array' && 0 < config.length){
res.status(200).send(config);
} else {
res.status(404).send();
}
});
}
I would also suggest that you should simply use the getItem query instead of scan:
http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#getItem-property

Answer 3

Since the config object keys value is one when result is not found so what you can do is check the length of keys of that object like this :
if ( Object.keys(config).length == 1 )return res.status(400).send("Error 404");