Adapted from purescript-logging
The stable version is tested against TypeScript 3.1.6, but should run with TypeScript 2.8.0+ too
From purescript-logging's README
A logger receives records and potentially performs some effects. You can create a logger from any function
(a: A) => HKT<M, void>for anyAandM.Unlike most other logging libraries,
logging-tshas no separate concepts "loggers" and "handlers". Instead, loggers can be composed into larger loggers using theSemigroupinstance. Loggers can also be transformed usingcontramap(for transforming records) andfilter(for filtering records). An example use case might be the following:
import { io } from 'fp-ts/lib/IO'
import * as L from 'logging-ts'
import * as C from 'fp-ts/lib/Console'
import * as D from 'fp-ts/lib/Date'
type Level = 'Debug' | 'Info' | 'Warning' | 'Error'
interface Entry {
message: string
time: Date
level: Level
}
const showEntry = (entry: Entry): string => `[${entry.level}] ${entry.time.toLocaleString()} ${entry.message}`
const getEntryLogger = (prefix: string) => {
return new L.Logger((entry: Entry) => C.log(`${prefix}: ${showEntry(entry)}`))
}
const filter = L.filter(io)
const debugLogger = filter(getEntryLogger('debug.log'), e => e.level === 'Debug')
const productionLogger = filter(getEntryLogger('production.log'), e => e.level !== 'Debug')
const logger = L.getSemigroup(io)<Entry>().concat(debugLogger, productionLogger)
const log = L.log(logger)
const info = (message: string) => (time: Date) => log({ message, time, level: 'Info' })
const debug = (message: string) => (time: Date) => log({ message, time, level: 'Debug' })
const program = D.create
.chain(info('boot'))
.chain(() => D.create)
.chain(debug('Hello!'))
program.run()
/*
production.log: [Info] 2017-10-17 10:14:21 boot
debug.log: [Debug] 2017-10-17 10:14:21 Hello!
*/