Go Fish: Functional State with React Hooks 🎣

Image of a fish hook. So original right?

Why use Hooks?

  1. Reduce the need for more than one type of component (no more class components)
  2. Save time refactoring components to add state
  3. Make components more readable
  4. Break application logic into reusable peices (custom hooks)
  5. No more dealing with the intricacies of the JavaScript ‘this’ object

Implementing State with Hooks

Common Types of Hooks

1. The State Hook

import React, { useState } from 'react';function CounterExample() {
const [count, setCount] = useState(0);
return (
<div>
<p>You clicked {count} times</p>
<button onClick={() => setCount(count + 1)}>
Click me
</button>
</div>
);
}

To use the useState hook, you first have to declare it. Typically it's destructed like this in the example. The first item in the array is state and can be given a variable like this one ‘count’. The second item in the array gives you a method to change the state, which you can also name, like ‘setCount’. useState takes one arguement which sets the value of the state. We are setting the initial count to 0 for 0 clicks.

2. The Use Effect Hook

import React, { useState, useEffect } from 'react';function CounterExample() {
const [count, setCount] = useState(0);
useEffect(() => {
document.title = `You clicked ${count} times`;
});
return (
<div>
<p>You clicked {count} times</p>
<button onClick={() => setCount(count + 1)}>
Click me
</button>
</div>
);
}

In this example, when the component was mounted, the useEffect hook set the document title to include the state of the count.

3. The Custom Hook

import { useState, useEffect } from 'react';

function useFriendStatus(friendID) {
const [isOnline, setIsOnline] = useState(null);
useEffect(() => {
function handleStatusChange(status) {
setIsOnline(status.isOnline);
}
ChatAPI.subscribeToFriendStatus(friendID, handleStatusChange);
return () => {
ChatAPI.unsubscribeFromFriendStatus(friendID,
handleStatusChange);
};
});

return isOnline;
}

The first thing you notice about this is that it looks just like a functional React component! The key difference between a custom hook and a component is that a component returns jsx to add to the DOM, while a custom hook is a function that can be imported to any function and used throught the application without passing any props. Let’s looks at an example of using a custom hook:

import React from 'react';
import useFriendStatus from ‘./useFriendStatus’;
function FriendListItem(props) {
const isOnline = useFriendStatus(props.friend.id);
return (
<li style={{ color: isOnline ? 'green' : 'black' }}>
{props.friend.name}
</li>
);
}

I hope this demystifyed hooks for you, especially custom hooks (they’re just functions!!) As always, thanks for reading 🦜

Resources:

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Full-Stack Software Engineer, Designer, and salsa dancer.

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