nodejs event source

eventSource.js

class EventSource extends EventEmitter {
    _lastEventID;
    _event = {
        data: '',
        eventType: '',
        dispatch() {
            super.emit(
                this.eventType ? this.eventType : 'message',
                this.data.endsWith('\n') ? this.data.slice(0, -1) : this.data
            );
            this.eventType = this.data = '';
        },
    };

    constructor(options) {
        super();
        Object.setPrototypeOf(this._event, this);
        this.req = https.request(options, (res) => {
            const eventSourceLines = readline.createInterface({ input: res });

            eventSourceLines.on('line', (l) => {
                this._dispatchOnLine(l);
            });
        });

        this.req.end();
    }

    //ref https://html.spec.whatwg.org/multipage/server-sent-events.html
    _evalField(field, value) {
        const field_dispatch = {
            event: () => {
                this._event.eventType = value;
            },
            data: () => {
                this._event.data += value + '\n';
            },
            id: () => {
                this._lastEventID = value;
            },
            retry() {},
        };

        field in field_dispatch ? field_dispatch[field]() : (() => {})();
    }

    _dispatchOnLine(evtLine) {
        //first dispatch on first char in line
        if (evtLine.length === 0) {
            //emit accumulated event
            this._event.dispatch();
        } else if (evtLine[0] === ':') {
            (() => {})();
        } else if (evtLine.includes(':')) {
            const indexOfColon = evtLine.indexOf(':');
            const field = evtLine.slice(0, indexOfColon);
            const value = evtLine.slice(indexOfColon + 1).trimStart();
            this._evalField(field, value);
        } else {
            this._evalField(evtLine, '');
        }
    }
}

simple nodejs based eventsource client implementation

MIT licensed.