Unable to get helper function to work in AWS lambda nodejs - node.js

Question

I'm new to nodejs and learning, but can't find out why my helper function won't work.
Essentially this is part of an example alexa lambda function that generally works.
The MQTT operation works if I leave the MQTTcode within the Intent handler, but I need to move it out into the main body of code so I can call the MQTT operation from other code functions.
There are several 'test' functions in this snippet that fail to work, probably because I don't appreciate the correct way to move the code out of the Intent function.
I'm also pretty unclear on handlers.. ( multiple handlers actually ) There are two handlers in the code snippet.. it doesn't cause a problem, but I was hoping to have two lambda triggers ( ask-sdk & smart home) with each calling their own handler - not sure if that's possible.
var APP_ID = "amzn1.ask.skill.xxxxxxxxxxxxxxxxxxxxxxxxxxxxx"; // input the axela skill ID
var AWS = require('aws-sdk');
var Alexa = require("alexa-sdk");
AWS.config.region = "us-east-1";
var iotData = new AWS.IotData({endpoint: "xxxxxxxxxxx.iot.us-east-1.amazonaws.com"}); // input the AWS thing end point
var topic = "esp32/sub"; //input the topic that the device is subscribed to
// Handler for Generic Event handling accepts both SmartHomeand ask-sdk events
// But only works when the handler below is removed.
exports.handler = async function (event, context) {
// Dump the request for logging - check the CloudWatch logs
console.log("index.handler request -----");
console.log(JSON.stringify(event));
if (context !== undefined) {
console.log("index.handler context -----");
console.log(JSON.stringify(context));
}
switchon(); // test call of standalone MQTTfunction ( doesn't work)
};
// Remove this function and the Smarthome Test works.
// But is needed for the ask-sdk events ( Smarthome events fail )
exports.handler = function(event, context, callback) {
var alexa = Alexa.handler(event, context);
alexa.appId = APP_ID;
alexa.registerHandlers(handlers);
alexa.execute();
console.log("index.handler comment -----");
};
//*********************************
// Helper code examples to functionalise the MQTT switch on
// NONE OF THESE WORK WHEN CALLED
function switchon3(){
var dataObj = {
topic: topic,
payload: "on",
qos:0
};
iotData.publish(dataObj, function (err, data) {
if (err) console.log(err, err.stack); // an error occurred
else console.log(data); // successful response
});
}
function switchon (error, data){
var params = {
topic: topic,
payload: "on",
qos:0
};
iotData.publish(params, (error, data)=>{
if (!error){this.emit(':tell', 'Robert, well done its Switched On');
}else{this.emit(':tell', 'Oh dear MQTT returned a switch on error')}
});
}
// End of helper examples
//*********************************
//********* THE PROPER CODE ************************
var handlers = {
'LaunchRequest': function () {
this.emit(':tell', 'Hello. Skill four here. How may I help you?');
},
'SwitchOnIntent': function () {
// None of the example function calls work here
// switchon3();
// this.emit(':tell', 'Test Switch On'); // needs this line to work
// The following original example code DOES work
var params = {
topic: topic,
payload: "on",
qos:0
};
iotData.publish(params, (error, data)=>{
if (!error){this.emit(':tell', 'Robert, well done its Switched On');
}else{this.emit(':tell', 'Oh dear MQTT returned a switch on error')}
});
},
Edited...
No, Tommy, it's not too basic, thanks for the help. I'm actually trying to get the lambda to accept inputs from two AWS triggers.
1. The ASK-API from custom skills
2. The Smarthome trigger.
I'm unsure if the two triggers need separate handler functions, or, if as I suspect, using the smarthome trigger voids the use of the ask-api methods that somehow call the registered Intent functions,
The json that arrives is clearly formatted differently from both trigger types, and I appreciate that it's possible to do all the alexa custom skill parsing manually within the lambda.
My question is then.. if starting out with a custom skill, registering all the function calls with the ask-api becomes void if I then add a smarthome trigger because the one handler that dealt with the ask-api event cannot also deal with the smarthome directive.
Subsequent to sorting that out, is trying to 'bring out' the MQTT call, that works within the Intent functions as originally coded, but fails if I try to put them into separate function calls.
Bear with me ... I know what I want to do.. just don't know this language well at all yet.

Answer 1

I think what you're not grasping here is that your actually overwriting the same variable.
exports is an object (variable) and it can have multiple properties. Forgive me if this is too basic, but a property is basically a variable attached to another variable.
In your code, you first assign the value of this property to a function.
exports.handler = async function (event, context) {
// Dump the request for logging - check the CloudWatch logs
console.log("index.handler request -----");
console.log(JSON.stringify(event));
if (context !== undefined) {
console.log("index.handler context -----");
console.log(JSON.stringify(context));
}
switchon(); // test call of standalone MQTTfunction ( doesn't work)
};
so if you then ran exports.handler() it would run that function. However, you then reassign this variable a few lines down.
So it's now the below:
exports.handler = function(event, context, callback) {
var alexa = Alexa.handler(event, context);
alexa.appId = APP_ID;
alexa.registerHandlers(handlers);
alexa.execute();
console.log("index.handler comment -----");
};
You are replacing the first function with the second one, which is why commenting out the second assignment to exports.handler causes the first bit to work. I'm not 100% clear on what you're asking, but you either need to combine the contents of both functions if you can (or have one handler that checks the event and calls a separate function), or move them into separate lambdas.
For instance:
exports.handler = function(event,context,callback) {
if(event.EventType === "YourGenericEvent") { // replace YourGenericEvent with whatever the eventName is for the first function
genericEvent(event,context)
} else if(event.EventType === "SecondEvent") { // again replace "SecondEvent" with whatever the event is for your second function
secondEvent(event,context,callback)
}
}
function genericEvent (event, context) {
// Dump the request for logging - check the CloudWatch logs
console.log("index.handler request -----");
console.log(JSON.stringify(event));
if (context !== undefined) {
console.log("index.handler context -----");
console.log(JSON.stringify(context));
}
switchon(); // test call of standalone MQTTfunction ( doesn't work)
};
function secondEvent(event,context,callback) {
var alexa = Alexa.handler(event, context);
alexa.appId = APP_ID;
alexa.registerHandlers(handlers);
alexa.execute();
console.log("index.handler comment -----");
}
your console.log(event) statements should hopefully give you an indication of what the value of the EventType property should be for the IF statements.
You can see another post related to Python here
How to have more than one handler in AWS Lambda Function?