Error Handling in a Recursive setTimeout Function in Node.js - node.js

Question

I'm building my first node.js application on my Raspberry Pi which I am using to control an air conditioner via LIRC. The following code is called when you want to increase the temperature of the AC unit. It sends a LIRC command every 250 milliseconds depending on how many degrees you want to increase it by. This code works as expected.
var iDegrees = 5;
var i = 0;
var delay = 250 // The delay in milliseconds
function increaseTemperatureLoop(){
i++;
//lirc_node.irsend.send_once("ac", "INCREASE", function() {});
console.log(i);
// Call the fucntion/loop again after the delay if we still need to increase the temperature
if (i <= iDegrees){
timer = setTimeout(increaseTemperatureLoop, delay);
}
else {
res.json({"message": "Success"});
}
}
// Start the timer to call the recursive function for the first time
var timer = setTimeout(increaseTemperatureLoop, delay);
I'm having a hard time working with the asynchronous nature of node.js. Once my recursive function is done, I return my json to the browser as shown in the code above. By habit, I feel like I should return the json in a line of code after my initial function call like below but obviously that wouldn't wait for all of the LIRC calls to be successful - it seems silly to have it inside of the function:
var timer = setTimeout(increaseTemperatureLoop, delay);
res.json({"message": "Success"});
What if I have a bunch of other stuff to do after my LIRC sends are done but before I want to send my json back to the browser? Or what if that block of code throws an error...
My second question is, how do I properly wrap the LIRC call in a try/catch and then if there is an error, stop the recursive calls, pass the error back up, and then pass this back to the browser along with the actual error message:
res.json({"message": "Failed"});

Answer 1

For track end of the cycle execution task, you can use a callback.
In order to know whether completed all routine tasks, you can use the task queue.
Monitor and report bugs to the top - it is possible with the help of
three of the same callback.
In general, it is desirable to wrap everything into a single object.
Some example for reflection:
var lircTasks = function __self (){
if (typeof __self.tasks === "undefined") __self.tasks = 0;
__self.func = {
increaseTemperature: function() {
// lirc_node.irsend.send_once("ac", "INCREASE_TEMPERATURE", function() {});
},
increaseFanPower: function() {
// lirc_node.irsend.send_once("ac", "INCREASE_FANPOWER", function() {});
}
}
var fab = function () {
__self.tasks++;
this.i = 0;
this.args = arguments[0];
this.callback = arguments[1];
this.run = function __ref(taskName) {
if (taskName) this.taskName = taskName;
if (this.i<this.args.deg) {
try {
__self.func[this.taskName]();
} catch(e) {
__self.tasks--;
this.callback( {message: "error", error: e, taskName: this.taskName, task: this.args, tasks: __self.tasks} );
}
this.i++;
setTimeout( __ref.bind(this), this.args.delay );
} else {
__self.tasks--;
this.callback({message:"complete", taskName: this.taskName, task: this.args, tasks: __self.tasks});
}
}
}
if ((arguments.length === 2) && (typeof arguments[1] === "function") && arguments[0].deg>0 && arguments[0].delay>=0) {
return new fab(arguments[0], arguments[1]);
}
}
function complete(e) {
console.log(e);
if (e.tasks === 0) console.log({message: "Success"});
}
lircTasks( {deg: 10, delay:100, device: "d1" }, complete ).run("increaseTemperature");
lircTasks( {deg: 20, delay:150, device: "d2" }, complete ).run("increaseTemperature");
lircTasks( {deg: 5, delay:100, device: "d3" }, complete ).run("increaseFanPower");