jquery $.getScript() replacement with vanilla JavaScript

getScript.js

"use strict";

// src: https://stackoverflow.com/a/28002292
const getScript = (source, callback) => {
    var script = document.createElement('script');
    var prior = document.getElementsByTagName('script')[0];
    script.async = 1;

    script.onload = script.onreadystatechange = (_, isAbort) => {
        if (isAbort || !script.readyState || /loaded|complete/.test(script.readyState)) {
            script.onload = script.onreadystatechange = null;
            script = undefined;
            if (!isAbort) if (callback) callback();
        }
    };

    script.src = source;
    prior.parentNode.insertBefore(script, prior);
};

This doesn't set the request header "accept" to be identical to what jquery does