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shouldComponentUpdate(nextProps, nextState) {
  let shouldUpdate = this.props.status !== nextProps.status;
  return shouldUpdate;
}

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type Snapshot = number | null;

class ScrollingList extends React.Component<Props, State, Snapshot> {
  listRef = React.createRef();

  getSnapshotBeforeUpdate(
    prevProps: Props,
    prevState: State
  ): Snapshot {
    // Are we adding new items to the list?

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componentWillUnmount() {
  this.chart.destroy();
  this.resetLocalStorage();
  this.clearSession();
}

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render() {
    return (
      <div>
        <Brick/> <Brick/> <Brick/> <Brick/> <Brick/> <Brick/> <Brick/> <Brick/>
        <Brick/> <Brick/> <Brick/> <Brick/>
      </div>
    )
  }

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import React, { Component } from 'react'

export default class Counter extends Component {
  constructor(props) {
    super(props);
    this.state = {
      counter: 0
    }
    this.handleCounter = this.handleCounter.bind(this);
  }

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import React, { useState } from 'react';
export default function counterHook() {
  const [count, setCount] = useState(0);
  return (
    <div>
      <div>
        <button onClick={() => setCount(count + 1)}> + Increment</button>
        <button onClick={() => setCount(count - 1)}> - Decrement</button>
      </div>
      <div>

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const countVariables = useState(0); // return two items in an array
const count = countVariables[0]; // first item from array
const setCount = countVariables[1]; // second item from array

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const [count, setCount] = useState(0);

// e.g const [a, b] = [1, 2]
// The value of a is 1
// The value of b is 2
// This is array destructuring

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const [count, setCount] = useState(0);
const [todos, setTodos] = useState(['Learn Hooks', 'Implement hooks']);
const [cart, setCart] = useState({id: 'xx22', name: 'iphone 8', quantity: 1});

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import React, { Component } from 'react'

export default class Counter extends Component {
  constructor(props) {
    super(props);
    this.state = {
      counter: 0
    }
    this.handleIncrement = this.handleCounter.bind(this);
  }