Simple Logger.ts

gistfile1.ts

const stringToBool = (s: string) => (s.toString().match(/^(true|[1-9][0-9]*|[0-9]*[1-9]+|yes)$/i) ? true : false)

type levelNames = "emerg" | "alert" | "crit" | "error" | "warn" | "notice" | "info" | "debug"
type logLevel = {
  name: levelNames
  cb: CallableFunction
  defaultEnabled: boolean
}
type callableNames = {
  [K in levelNames]: CallableFunction
}
type levelsEnabled = { [Property in levelNames]?: boolean }

// info and debug are disabled by default.
const logLevelsN: logLevel[] = [
  { name: "emerg", cb: console.error, defaultEnabled: stringToBool(process.env?.REACT_APP_LOG_EMERG ?? "true") },
  { name: "alert", cb: console.warn, defaultEnabled: stringToBool(process.env?.REACT_APP_LOG_ALERT ?? "true") },
  { name: "crit", cb: console.error, defaultEnabled: stringToBool(process.env?.REACT_APP_LOG_CRIT ?? "true") },
  { name: "error", cb: console.error, defaultEnabled: stringToBool(process.env?.REACT_APP_LOG_ERROR ?? "true") },
  { name: "warn", cb: console.warn, defaultEnabled: stringToBool(process.env?.REACT_APP_LOG_WARN ?? "true") },
  { name: "notice", cb: console.log, defaultEnabled: stringToBool(process.env?.REACT_APP_LOG_NOTICE ?? "true") },
  { name: "info", cb: console.info, defaultEnabled: stringToBool(process.env?.REACT_APP_LOG_INFO ?? "false") },
  { name: "debug", cb: console.debug, defaultEnabled: stringToBool(process.env?.REACT_APP_LOG_DEBUG ?? "false") }
] as const

/**
 * This is a simple logger, which outputs the right path in console (where its called from parent).
 * There is multiple ways to configure this (further down overwrites further up)
 * - You can toggle levels globally via .env (REACT_APP_LOG_DEBUG = false). Remember to rerun 'yarn run start'.
 * - You can pass settings in the constructor: { enabled: { debug: false } } if you want to hide output from debug.
 * - You can overwrite it for your instance like myLogger.enabled.debug = false
 */
export const Logger = class implements callableNames {
  emerg: CallableFunction
  alert: CallableFunction
  crit: CallableFunction
  error: CallableFunction
  warn: CallableFunction
  notice: CallableFunction
  info: CallableFunction
  debug: CallableFunction

  private enStore: levelsEnabled
  enabled: levelsEnabled

  constructor(props?: { prefix?: string; enabled?: levelsEnabled }) {
    this.emerg = this.alert = this.crit = this.error = this.warn = this.notice = this.info = this.debug = () => 0
    this.enStore = props?.enabled ?? {}
    // whenever somebody sets a key like enabled.debug we re-apply the appropriate function.
    this.enabled = new Proxy(this.enStore, {
      set: (target, lvlName: levelNames, value) => {
        this[lvlName] = value
          ? Function.prototype.bind.call(
              Logger.getLvl(lvlName).cb,
              console,
              `%c${props?.prefix ?? ""}(${lvlName})`,
              "color: color-mix(in srgb, currentColor 55%, transparent)"
            )
          : () => 0
        return true
      }
    })
    // add the functions for all enabled levels.
    logLevelsN.forEach((lvl) => {
      // apply defaults to all enabled-levels => this triggers the proxy to set the functions.
      this.enabled[lvl.name] = undefined === this.enStore?.[lvl.name] ? lvl.defaultEnabled : this.enStore[lvl.name]
    })
  }
  // @todo: logLevelsN should probably be a record, so we don't have this issue...
  static getLvl(lvlName: levelNames): logLevel {
    const found = logLevelsN.find((lvl) => lvlName === lvl.name)
    if (found === undefined) {
      throw new TypeError("The value was promised to always be there!")
    }
    return found
  }
}