ReactJS "TypeError: Cannot read property 'array' of undefined"

Prop-Types are now a separately maintained library named prop-types Here is the explanation from react-docs: https://reactjs.org/docs/typechecking-with-proptypes.html

You have to import them as

import React from 'react';
import PropTypes from 'prop-types'

class App extends React.Component {
  //App here
}

App.propTypes = {
 propArray: PropTypes.array.isRequired, 
 propBool: PropTypes.bool.isRequired,
 propFunc: PropTypes.func,
 propNumber: PropTypes.number,
 propString: PropTypes.string,
 propObject: PropTypes.object
}

NPM Package

Change this:

App.propTypes = {
   propArray: React.PropTypes.array.isRequired, //I got error over here
   propBool: React.PropTypes.bool.isRequired,
   propFunc: React.PropTypes.func,
   propNumber: React.PropTypes.number,
   propString: React.PropTypes.string,
   propObject: React.PropTypes.object
}

to:

App.propTypes = {
  propArray: PropTypes.array.isRequired,
  propBool: PropTypes.bool.isRequired,
  propFunc: PropTypes.func,
  propNumber: PropTypes.number,
  propString: PropTypes.string,
  propObject: PropTypes.object
}`