import * as log from "@thi.ng/rstream-log";
import { writeFile } from "@thi.ng/rstream-log-file";

const logger = new log.Logger("main");

// add file output w/ post-filtering (only WARN or ERROR levels)
// and formatted as JSON
const writer = logger
    .transform(log.minLevel(log.Level.WARN), log.formatJSON())
    .subscribe(writeFile("main.log"));

logger.warn("eek!");

// appended to file:
// {"level":"WARN","id":"main","time":"2018-01-23T09:05:55.647Z","body":["eek!"]}

// optionally, cancel file writer
writer.done();