emilong

const x = { a: 1 }
x.a = 2       // legit! the object itself is mutable
x.b = 3       // legit! the object itself is mutable
              // x = { a: 2, b: 3 }

const a = [1]
a.pop()       // legit! the array itself is mutable
a.push(2)     // legit! the array itself is mutable
              // a = [2]

emilong

const optionalParam = (maybe) => {
  // when falsey values aren't allowed, this will work
  const definitely = maybe || 'oasis'

  // ...
}

const optionalOption = (options) => {
  // defaults in destructuring
  const { definitely='oasis' } = options

emilong

function helper(input) {
  // ...do some complicated logic

  return 'some result of the complicated logic' + input
}

const delegator = (arg) => {
  // just move the complicated decision logic to a helper function
  const definitely = helper(arg)

emilong

const neverGonnaModifyYou = Object.freeze({ a: 3 })
neverGonnaModifyYou.a = 4   // Won't throw, at least on node, chrome, ff & safari, but will leave the value intact
neverGonnaModifyYou.b = 4   // Won't throw, at least on node, chrome, ff & safari, but will leave the value intact
                            // neverGonnaModifyYou === { a: 3 }

const neverGonnaLetYouPop = Object.freeze([1])
neverGonnaLetYouPop.pop()   // throws!
neverGonnaLetYouPop.push(2) // throws!

emilong

const { createSelector } = require('reselect')
const { every } = require('lodash')

function greaterThan2(x) {
  return x > 2
}

function even(x) {
  return x % 2 === 0
}

emilong

import { combineReducers } from 'redux'
import { createAction, handleActions } from 'redux-actions'

const listFetched = createAction('ITEM_LIST_FETCHED')

const itemReducer = handleActions({
  ITEM_LIST_FETCHED: (state, action) => {
    // the payload of the action is just a list of the items,
    // each of which may have an id
    return action.payload

emilong

import { find } from 'lodash'
import React, { Component } from 'react'
import { connect } from 'react-redux'

class WetComponent extends Component {
  // ... do something with an item
}

const mapStateToProps = (state, ownProps) => {
  // assume we're using redux-router

emilong

import { find } from 'lodash'
import { combineReducers } from 'redux'
import { createAction, handleActions } from 'redux-actions'

const listFetched = createAction('ITEM_LIST_FETCHED')

const itemReducer = handleActions({
  ITEM_LIST_FETCHED: (state, action) => {
    // the payload of the action is just a list of the items,
    // each of which may have an id

emilong

import { find } from 'lodash'
import { combineReducers } from 'redux'
import { createAction, handleActions } from 'redux-actions'

const listFetched = createAction('ITEM_LIST_FETCHED')

const itemReducer = handleActions({
  ITEM_LIST_FETCHED: (state, action) => {
    // the payload of the action is just a list of the items,
    // each of which has an id

emilong

import { combineReducers } from 'redux'
import { createAction, handleActions } from 'redux-actions'

const authorFetched = createAction('AUTHOR_FETCHED')
const bookFetched   = createAction('BOOK_FETCHED')

const literaryReducer = handleActions({
  // maybe an author has a bunch of books as sub-resources
  AUTHOR_FETCHED: (state, action) => {
    const author = action.payload