Check if Express request data is array

Question

I've working on an Express 3.x API server (don't ask why I'm not upgrading to 4.x; I'm not in control of that), and I'm trying to implement support for batch requests for a particular endpoint. The endpoint currently supports regular requests (takes a JSON object), but I want it to also be able to take array of JSON objects, e.g.:

POST /api/posts
Body:
[
  { "title": "Hello World", "text": "blah blah" },
  { "title": "Hello World 2", "text": "blah blah blah" }
]

When I try to access the body of the request for a single request using req.body, I can retrieve the data just fine (it's just a regular JSON object). However, when I send an array, I find that the data gets parsed as an object of objects(?) instead of an array.

req.body = { "title": "Hello World", "text": "blah blah" };
typeof req.body;
// object
req.body.toString();
// [object Object]

req.body = [
  { "title": "Hello World", "text": "blah blah" },
  { "title": "Hello World 2", "text": "blah blah blah" }
];
typeof req.body;
// object
req.body.toString();
// [object Object],[object Object]

I tried using a simple check like this:

if (req.body.toString() !== '[object Object]') {

But an array containing only one object breaks this. E.g.:

req.body = [{ "title": "Hello World", "text": "blah blah" }];
typeof req.body;
// object
req.body.toString();
// [object Object]

Given this, is there guaranteed way to check to see if my data is an array?

Answer 1

The typical way to do this in any JavaScript environment would be:

if ( req.body instanceof Array ) {
    // do stuff
}

But since you have the luxury of your JavaScript running inside of V8, you could also use the following without any issues:

if ( Array.isArray(req.body) ) {
    // do stuff
}

Just personal preference on which one you use.