express-middleware.html

<script>
    class ExpressMiddleware extends HTMLElement {
        constructor() {
            super();

            this.method = null;
            this.path = null;
            this.callback = null;
            this.callbacks = null;
            this.app = null;
            this.router = null;
            this.route = null;
        }

        static get observedAttributes() {
            return [
                'method',
                'path'
            ];
        }

        attributeChangedCallback(name, oldValue, newValue) {
            switch (name) {
                case 'method': {
                    this.method = newValue;
                    break;
                }
                case 'path': {
                    this.path = newValue;
                    break;
                }
            }
        }

        expressReadyCallback(app, express, router, route) {
            this.app = app;
            this.router = router;
            this.route = route;

            if (this.callback) {
                this.initRouteWithCallback();
                return;
            }

            if (this.callbacks) {
                this.initRouteWithCallbacks();
                return;
            }
        }

        initRouteWithCallback() {
            if (this.method) {

                if (!this.path) {
                    throw 'ExpressMiddlewareError: specifying a method requires specifying a path';
                }

                if (this.route) {
                    this.route[this.method.toLowerCase()](this.callback);
                }
                else if (this.router) {
                    this.router[this.method.toLowerCase()](this.path, this.callback);
                }
                else {
                    this.app[this.method.toLowerCase()](this.path, this.callback);
                }

                return;
            }

            if (this.path) {
                if (this.router) {
                    this.router.use(this.path, this.callback);
                }
                else {
                    this.app.use(this.path, this.callback);
                }

                return;
            }

            if (this.router) {
                this.router.use(this.callback);
            }
            else {
                this.app.use(this.callback);
            }
        }

        initRouteWithCallbacks() {

            if (this.method) {

                if (this.route) {
                    this.route[this.method.toLowerCase()](...this.callbacks);
                }
                else if (this.router) {
                    this.router[this.method.toLowerCase()](this.path, ...this.callbacks);
                }
                else {
                    this.app[this.method.toLowerCase()](this.path, ...this.callbacks);
                }

                return;
            }

            if (this.path) {

                if (this.router) {
                    this.router.use(this.path, ...this.callbacks);
                }
                else {
                    this.app.use(this.path, ...this.callbacks);
                }

                return;
            }

            if (this.router) {
                this.router.use(...this.callback);
            }
            else {
                this.app.use(...this.callback);
            }
        }
    }

    window.customElements.define('express-middleware', ExpressMiddleware);
</script>