Logger for Redux

Install

npm i --save redux-logger

Usage

import { applyMiddleware, createStore } from 'redux';
import thunk from 'redux-thunk';
import promise from 'redux-promise';
import createLogger from 'redux-logger';

const logger = createLogger();
const createStoreWithMiddleware = applyMiddleware(thunk, promise, logger)(createStore);
const store = createStoreWithMiddleware(reducer);

Logger must be last middleware in chain, otherwise it will log thunk and promise, not actual actions (#20).

API

redux-logger exposes single constructor function for creating logger middleware.

createLogger(options?: Object) => LoggerMiddleware

Options

level (String)

Level of console. warn, error, info or else.

Default: log

duration (Boolean)

Print duration of each action?

Default: false

timestamp (Boolean)

Print timestamp with each action?

Default: true

colors (Object)

Object with color getter functions: title, prevState, action, nextState, error. Useful if you want to paint message based on specific state or action. Set any of them to false if you want to show plain message without colors.

• title(action: Object) => color: String
• prevState(prevState: Object) => color: String
• action(action: Object) => color: String
• nextState(nextState: Object) => color: String
• error(error: Any, prevState: Object) => color: String

logger (Object)

Implementation of the console API. Useful if you are using a custom, wrapped version of console.

Default: window.console

logErrors (Boolean)

Should the logger catch, log, and re-throw errors? This makes it clear which action triggered the error but makes "break on error" in dev tools harder to use, as it breaks on re-throw rather than the original throw location.

Default: true

collapsed = (getState: Function, action: Object) => Boolean

Takes a boolean or optionally a function that receives getState function for accessing current store state and action object as parameters. Returns true if the log group should be collapsed, false otherwise.

Default: false

predicate = (getState: Function, action: Object) => Boolean

If specified this function will be called before each action is processed with this middleware. Receives getState function for accessing current store state and action object as parameters. Returns true if action should be logged, false otherwise.

Default: null (always log)

stateTransformer = (state: Object) => state

Transform state before print. Eg. convert Immutable object to plain JSON.

Default: identity function

actionTransformer = (action: Function) => action

Transform action before print. Eg. convert Immutable object to plain JSON.

Default: identity function

errorTransformer = (error: Any) => error

Transform error before print.

Default: identity function

Recipes

log only in dev mode

import thunk from 'redux-thunk';

const middlewares = [thunk];

if (process.env.NODE_ENV === `development`) {
  const createLogger = require(`redux-logger`);
  const logger = createLogger();
  middlewares.push(logger);
}

const store = compose(applyMiddleware(...middlewares))(createStore)(reducer);

log everything except actions with type AUTH_REMOVE_TOKEN

createLogger({
  predicate: (getState, action) => action.type !== AUTH_REMOVE_TOKEN
});

collapse actions with type FORM_CHANGE

createLogger({
  collapsed: (getState, action) => action.type === FORM_CHANGE
});

transform Immutable objects into JSON

const stateTransformer = (state) => {
  let newState = {};

  if (typeof state === "object" && state !== null && Object.keys(state).length) {
    for (var i of Object.keys(state)) {
      if (Immutable.Iterable.isIterable(state[i])) {
        newState[i] = state[i].toJS();
      } else {
        newState[i] = stateTransformer(state[i]);
      }
    }
  } else {
    newState = state;
  }

  return newState;
}

const logger = createLogger({
  stateTransformer,
});

log batched actions

Thanks to @smashercosmo

import createLogger from 'redux-logger';

const actionTransformer = action => {
  if (action.type === 'BATCHING_REDUCER.BATCH') {
    action.payload.type = action.payload.reduce((result, next) => {
      const prefix = result ? result + ' => ' : '';
      return prefix + next.type;
    }, '');

    return action.payload;
  }

  return action;
};

const level = 'info';

const logger = {};

for (const method in console) {
  if (typeof console[method] === 'function') {
    logger[method] = console[method].bind(console);
  }
}

logger[level] = function levelFn(...args) {
  const lastArg = args.pop();

  if (Array.isArray(lastArg)) {
    return lastArg.forEach(item => {
      console[level].apply(console, [...args, item]);
    });
  }

  console[level].apply(console, arguments);
};

export default createLogger({
  level,
  actionTransformer,
  logger
});

License

MIT