@meisterplayer/util-load-script/index.js

Load a remote script asynchronously

function addEvents(scriptNode, resolve, reject) {
    scriptNode.addEventListener('load', () => {
        scriptNode.setAttribute('scriptLoaded', '1');
        resolve();
    });

    scriptNode.addEventListener('error', () => {
        scriptNode.setAttribute('scriptError', '1');
        reject();
    });
}

export default function loadScript(name, src) {
    return new Promise((resolve, reject) => {
        // Check for duplicates.
        const scriptNode = document.getElementById(name);
        if (scriptNode) {
            // The scriptnode IS available but the promise keeps pending because the onload event is not triggered (since the script was already loaded)
            if (scriptNode.getAttribute('scriptLoaded') === '1') {
                // we still need to check if the onload-event was triggered previously because the promise could not be resolved (edge case when connection is slow)
                resolve();
            } else if (scriptNode.getAttribute('scriptError') === '1') {
                // Reject promise again, it errored previously, it's safe to assume it will error again
                reject();
            } else {
                // The same script was requested by another 
                addEvents(script, resolve, reject);
            }

            return;
        }

        const script = document.createElement('script');
        script.src = src;

        addEvents(script, resolve, reject);

        script.id = name;
        document.getElementsByTagName('body')[0].appendChild(script);
    });
}