keycloak_theme/src/tools/headInsert.ts

import "./HTMLElement.prototype.prepend";
import { Deferred } from "evt/tools/Deferred";

export function headInsert(
    params:
        | {
              type: "css";
              href: string;
              position: "append" | "prepend";
          }
        | {
              type: "javascript";
              src: string;
          }
): { remove: () => void; prLoaded: Promise<void> } {
    const htmlElement = document.createElement(
        (() => {
            switch (params.type) {
                case "css":
                    return "link";
                case "javascript":
                    return "script";
            }
        })()
    );

    const dLoaded = new Deferred<void>();

    htmlElement.addEventListener("load", () => dLoaded.resolve());

    Object.assign(
        htmlElement,
        (() => {
            switch (params.type) {
                case "css":
                    return {
                        "href": params.href,
                        "type": "text/css",
                        "rel": "stylesheet",
                        "media": "screen,print"
                    };
                case "javascript":
                    return {
                        "src": params.src,
                        "type": "text/javascript"
                    };
            }
        })()
    );

    document.getElementsByTagName("head")[0][
        (() => {
            switch (params.type) {
                case "javascript":
                    return "appendChild";
                case "css":
                    return (() => {
                        switch (params.position) {
                            case "append":
                                return "appendChild";
                            case "prepend":
                                return "prepend";
                        }
                    })();
            }
        })()
    ](htmlElement);

    return {
        "prLoaded": dLoaded.pr,
        "remove": () => htmlElement.remove()
    };
}