React Hooks

Hooks introduces State and Lifecycle Methods to function-based components.

Hooks make it really easy to share logic between components.

Some Basic Hooks

Before Hooks

// components/App.js
import React from 'react';

export default App extends React.Component {
    state = {
        counter: 0
    }

    handleClick = () => this.setState({counter: this.state.counter++})

    render() {
        return <div>
            <button onClick={this.handleClick}>{this.state.counter}</button>
        </div>
    }
}
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After Hooks

// components/App.js
import React, {useState, useEffect} from 'react';

const App = () => {
    const [counter, setCounter] = useState(0);

    const updateCounter = () => setCounter(counter++)

    useEffect(() => {
        console.log('Counter updated!');
    }, [counter]);

    return <div>
        <button onClick={updateCounter}>{counter}</button>
    </div>
}
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Lifecycles with useEffect

useEffect allows us to effectively use a combined version of componentDidMount and componentDidUpdate.

Notes:

import React, {useEffect} from 'react';

// second argument controls whether or not the arrow function is called
useEffect(() => {
    console.log('Counter updated!');
}, [counter]);
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Code Reuse Example

Believe it or not, what we can actually do is abstract the useEffect outside of the function component.

This is incredibly useful to create reuseable effects.