swc/crates/swc_ecma_minifier/tests/single-pass/6/input.js

export const loadScript = (options) => {
    const { id, onLoad = () => null, ...rest } = options;

    return new Promise((resolve) => {
        let scriptEl = document.getElementById(id);

        const isMounted = !!scriptEl;

        if (!scriptEl) {
            scriptEl = document.createElement("script");
            Object.keys(rest).forEach((key) => (scriptEl[key] = rest[key]));
            scriptEl.id = id;
            scriptEl.async = true;
            scriptEl.type = "text/javascript";
        }
        if (rest.src) {
            scriptEl.addEventListener("load", () => {
                onLoad();
                return resolve();
            });
        }

        if (!isMounted) {
            // when enabling swcMinify, this section won't be executed
            document.getElementsByTagName("head")[0].appendChild(scriptEl);
        }

        if (!rest.src) {
            onLoad();
            return resolve();
        }
    });
};