Stop Using && operator for Conditional Rendering in React

React is a very popular JavaScript front-end framework that helps you to create SPA apps and user interfaces.

Most of the developers can’t use && operator correctly. It will easily lead to UI rendering errors. In 2023 we need to know about:

1. React UI error caused by && operator
2. What we should use instead of && operator?

1. React UI error caused by && operator

Here in this example, I need to fetch users’ data from the API, which is used to render a user’s list. If the length of the usersList is 0, then it should not be displayed.

import React from 'react';
import axios from 'axios';

const App = () => {
  const [usersList, setUsersList] = React.useState([]);

  const fetchUsersList = () => {
    axios.get('/api/users')
      .then(response => {
        setList(response.data);
      })
      .catch(error => {
        console.error('Error fetching list:', error);
        setList([]);
      });
  };

  React.useEffect(() => {
    fetchUsersList();
  }, []);

  return (
    usersList.length && (
      <div className="name-list-container">
        {list.map((name) => (
          <div className="name-list-item">{name}</div>
        ))}
      </div>
    )
  );
};

You will notice that when usersList is an empty array, then the page will render a 0 instead of nothing.

2. What we should use instead of && operator?

We should avoid using the && operator if we give up using it. Because && operator makes it easy to make mistakes. We can use 3 ways to avoid this problem.

2.1 Use  !!usersList.length 

We can turn the length check to a boolean value and avoid this error. This time the error will not happen again

// 1. Convert list.length to boolean
!!usersList.length && <Component list={list} />

2.2 Use  !!usersList.usersList.length >= 1

We can use the length of the array into a boolean value and this error will not happen again.

// 2. Controlled by specific logic
usersList.length >= 1 && <Component list={list} />;

2.3 Using ternary expressions

We can use another method to turn it into a boolean value.

// 3. Use ternary expressions and null
usersList.length ? <Component list={list} /> : null;