How to get CSRF tokens in a React/Rails App? ActionController::InvalidAuthenticityToken - ruby-on-rails

Question

Before going into more detail about the title, I just want to describe the problem at a basic level. I'm getting the dreaded 422, Unprocessable Entity error (ActionController::InvalidAuthenticityToken) after asynchronous requests in my app. What's the best way to handle this?
Loads of answers will say do:
skip_before_action :verify_authenticity_token
(which is now skip_forgery_protection in Rails 6), and then usually in the comments people get way more upvotes asking about whether or not that's a security risk. There are probably 5 threads like that.
The alternatives to doing this though, is sending the csrf token along with the POST request. So, most answers say make sure to include these headers
'Content-Type': 'application/json',
'Accept': 'application/json',
'X-Requested-With': 'XMLHttpRequest'
and also a csrf token like:
'X-CSRF-Token': csrfToken
The issue is getting the csrf token itself. I've tried displaying the contents of the header object with
const getHeaders = () => {
let headers = new window.Headers({
'Content-Type': 'application/json',
'Accept': 'application/json',
'X-Requested-With': 'XMLHttpRequest'
})
const csrfToken = document.head.querySelector("[name='csrf-token']")
if (csrfToken) { headers.append('X-CSRF-Token', csrfToken) }
return headers
}
and
let headers = getHeaders();
headers.forEach(function(value, name) {
console.log(name + ": " + value);
});
and that doesn't work. I'm guessing however I'm actually getting the token isn't working. Namely:
document.head.querySelector("[name='csrf-token']")
What's the best way to do this with plain ol' JavaScript, no other libraries? I've tried other suggestions and methods to attempt to get the token but so far all have failed. I'm assuming this lives somewhere on my browser but where? I can see all the data in Redux dev tools so the issue is definitely just this token as opposed to sending the correct data correctly (not to mention skip_forgery_protection completely solves it).
In the mean time sadly skip_forgery_protection works perfectly fine added to my Rails controllers, as security isn't the biggest concern in this stage, but I would rather fix the token issue. Thanks!