perjansson

const transformer = (file, api) => {
   const j = api.jscodeshift;
   const root = j(file.source);

   const multiLineArrays = path => {
      const { loc } = path.node;
      return loc.start.line < loc.end.line;
   }

   return root

perjansson

const transformer = (file, api) => {
  /* get the jscodeshift helper */
  const j = api.jscodeshift;

  /* create a js object representation of your source code */
  const root = j(file.source);

  return root
    .find(/* grab the code you want to update */)
    .forEach(/* do something to it */)

perjansson

var CarList = React.createClass({
   getInitialState: function() { }
   setSelectedCar: function(selectedCar) { }
   ...
   
// becomes

class CarList extends React.Component {
   state = { }
   setSelectedCar = selectedCar => { }

perjansson

cars: [
   'Volvo',
   'BMW',
   'Tesla',
   'Lada'
]

// becomes

cars: [

perjansson

var state = { selectedCar: selectedCar }

// becomes

var state = { selectedCar }

perjansson

var state = Object.assign({}, state.history, selectedCar.id)

// becomes

var state = { ...state.history, ...selectedCar.id }

perjansson

var message = 'The best car is ' + randomCar

// becomes

var message = `The best car is ${randomCar}`

perjansson

onClick={function(e) {
   this.setSelectedCar(e.target.value)
}.bind(this)}

// becomes

onClick={e => this.setSelectedCar(e.target.value)}

perjansson

var cars = this.cars.map(car => ...
var message = 'No cars'
   if (cars.length) {
      var randomCar = null
      message = `The best car is ${randomCar}`
      ...
      
// becomes

const cars = this.cars.map(car => ...

perjansson

class ProgressiveImage extends Component {
  state = {
    currentImage: this.props.preview,
    loading: true,
  }

  componentDidMount() {
    this.fetchImage(this.props.image)
  }