vzaidman

const Main = React.memo(({onClick, style, children, items}) => {
  const content = getContent({items});
  return (
    <div style={style} onClick={onClick}>
      {content}
      {children}
    </div>
  );
})

vzaidman

// the hook
function useRefWithCallback(onMount, onUnmount) {
  const nodeRef = useRef(null);

  const setRef = useCallback(node => {
    if (nodeRef.current) {
      onUnmount(nodeRef.current);
    }

    nodeRef.current = node;

vzaidman

{
  "1164": "؋123,456.00 (Afghanistan)",
  "1052": "123,456.00 Lek (Albania)",
  "5121": "د.ج.‏ 123,456.00 (Algeria)",
  "11274": "$ 123,456.00 (Argentina)",
  "1067": "123,456.00 ֏ (Armenia)",
  "3081": "$123,456.00 (Australia)",
  "3079": "123,456.00 € (Austria)",
  "1068": "123,456.00 man. (Azerbaijan)",
  "2092": "123,456.00 ман. (Azerbaijan)",

vzaidman

import user from './user'

describe('user', () => {
  
  // before each test
  beforeEach(() => {
    // spy on the "isValid" function on the "user" object
    jest.spyOn(user, 'isValid');
  })
  

vzaidman

class Child {
  ...
  execute(arg) { ... }
  ...
}
  
class Father {
  constructor() {
    this.child = new Child()
  }

vzaidman

describe('My First Cypress Test', function() {
  it("Gets, types and asserts", function() {
    cy.visit('https://example.cypress.io')

    cy.contains('type').click()

    // Should be on a new URL which includes '/commands/actions'
    cy.url().should('include', '/commands/actions')

    // Get an input, type into it and verify that the value has been updated

vzaidman

// the hook
function useStateRef(processNode) {
  const [node, setNode] = useState(null);
  const setRef = useCallback(newNode => {
    setNode(processNode(newNode));
  }, [processNode]);
  return [node, setRef];
}

// how it's used

vzaidman

const [node, setRef] = useState(null);

useEffect(() => {
  if (!node) {
    console.log('unmounted!');
    return null;
  }
  
  console.log('mounted');
  

vzaidman

module.exports = require('../babel.config')

vzaidman

module.exports = {
  ...require('../jest.config'),
  rootDir: '..',
  cacheDirectory: '.cache/jest-cache-react-16',
  moduleDirectories: [
    '<rootDir>/test-react-16/node_modules',
    'node_modules'
  ]
}