Map Elements of an Array with ES2019 flatMap
ES2019 introduces the Array.prototype.flatMap method. In this lesson, we'll investigate a common use case for mapping and flattening a multidimensional array. We'll then see how to do this using Array.prototype.reduce, and then refactor the code to do the same thing using the ES2019 .flatMap method.
Great lesson!
Quick note - code below is showing:
averageCount() {
const counts =
this.records.forEach(record => {
counts.push(record.am, record.pm);
});
return average(counts)
},
Shouldn't counts be declared as follows?:
const counts = [];
Good catch Tony! It'll be fixed shortly. Thanks!
Looks like the typo @Tony Whomever pointed out is still present in the transcript.
I also noticed that in the video's description it references Array.prototype.reduce, but the actual code uses Array.prototype.forEach.
I like this new method. I've often encountered the problem of wanting to map one array to an array of a different size and being forced either to chain the map to a filter or just write a reduce. Those are both fine solutions, but flatMap looks like it might be more compact and economical, at least under certain conditions.
That being said, I wonder if it will become easy to abuse this method's flexibility and lose the clarity that the filter and reduce syntaxes provide. TBD.