API Consumer

We then employ the http module "get" function to call the API and pass along a reader (more on this next).

https
	.get(apiUrl, dataRecr.getReadDataFct())
	.on("error", errorCallback);

DataReceiver

We code a class DataReceiver class that is our workhorse.

Keep en eye on the "dataString" ivar, it is where we'll store the API data as we receive it.

class DataReceiver {

constructor(finishFct) {
	this.apiResult = null;
	this.dataString = '';
	this.finishFct = finishFct;
}

receive chunk

Nice simple method right.

This is where it all happens. For each chunk we receive from the API, this method is called and we append it to our ivar.

receiveNextChunk(chunk) {
	//console.log('chunk: ' + chunk);
	this.dataString += chunk;
}

finish receiving data

This method is called after we have received all the data from the API.

We use js' global JSON object to parse the string result -- the result of the parse is a friendly plain js object.

We then call the "finishFct" (the one that was provided to us when we were constructed).

finishReceivingData() {
	//console.log('dataString: ' + this.dataString);
	try {
		this.apiResult = JSON.parse(this.dataString);
		this.finishFct(this.apiResult);
	} catch(exception) {
		console.log(`Error calling API: ${this.dataString}`);
		throw exception;
	}
}

Use API Result

Now we do whatever we want with the data -- e.g., do calculations with it, render it onto HTML, etc.

To keep the example simple, here we print the results to the console.

static showApiResult(results) {
	//result is array of pairs {unit, value}
	//if not array, assume we have error
	if (!Array.isArray(results))
		log(results.toString());
	else
		results.forEach(pair => log(`${pair.value} ${pair.unit}`));
}

Output

After running the node app in the normal way, we should see output similar to this.

You will want to startup your API server before running your API consumer

Gotcha - if your editor does not allow you to run multiple web servers simultaneously, then simply start your programs from the console, e.g., "node my-progarm".

-- API Data Received --
2 m
6.56168 ft
2000 mm
200 cm
0.002 km
78.74016 in
0.00124 mi
2.18723 yd

Source Code

Here is the example project source code.

The project will not require a npm init nor npm install.