React Notes

Notes for starting React


The Component Lifecycle


These methods are called in the following order when an instance of a component is being created and inserted into the DOM:

  • constructor()
  • static getDerivedStateFromProps()
  • render()
  • componentDidMount()


An update can be caused by changes to props or state. These methods are called in the following order when a component is being re-rendered:

  • static getDerivedStateFromProps()
  • shouldComponentUpdate()
  • render()
  • getSnapshotBeforeUpdate()
  • componentDidUpdate()


This method is called when a component is being removed from the DOM:

  • componentWillUnmount()

Error Handling

These methods are called when there is an error during rendering, in a lifecycle method, or in the constructor of any child component.

  • static getDerivedStateFromError()
  • componentDidCatch()

ISSUE: Push a new route only triggers URL change but not location change

keywords: connected-react-router, redux-saga

Reasons: withRouter does not subscribe to location changes like React Redux’s connect does for state changes. Instead, re-renders after location changes propagate out from the component. This means that withRouter does not re-render on route transitions unless its parent component re-renders. If you are using withRouter to prevent updates from being blocked by shouldComponentUpdate, it is important that withRouter wraps the component that implements shouldComponentUpdate. So using withRouter to wrap connect to fix it.

Things wrong:

  • Using two different instances of history
  • Using both ConnectedRouter and BrowserRouter

Code to use withRouter and connect in App.tsx

// as any to escape type checking in typescript 
export default withRouter(connect(mapStateToProps, mapDispatchToProps)(withStyles(styles)(AppComponent)) as any);

Material UI

Reference defined styles ($)

  root: {
    '&:hover $icon': {
      transform: 'scale(2.8)',
  icon: {
    transform: 'scale(2.5)',

Clone element, attach properties and check element type using TypeScript (action: any)

const actions = [<h1 />, <IconButton><CloseIcon /></IconButton>];
actions.forEach((action: any, index) => {
  React.cloneElement(action, {
    key: `ACTION-${index}`,
    className: action.type === IconButton ? classes.headerToolboxButton : ''

Global styles for current page

  '@global': {
    a: {
      color: 'inherit',
    '.recharts-tooltip-label': {