Introduction

Authorization is a critical aspect of any web application, ensuring that users only have access to the features and data they are allowed to interact with. CASL (stands for "Capability-based Access Control") is a popular JavaScript library for handling this logic in a flexible and declarative way. In this article, we’ll walk through how to integrate CASL with a React application, providing you with the tools to implement effective authorization.

Prerequisites

Before diving into the integration, you should be familiar with the following:

Basic understanding of React.
Familiarity with state management in React.
Basic knowledge of JavaScript ES6+.

Step 1: Setting Up CASL

npm install @casl/ability @casl/react

Step 2: Defining Abilities

Abilities define what actions a user can perform on particular resources. Let’s start by creating an ability instance.

import { Ability } from '@casl/ability';

const defineAbilitiesFor = (user) => {
  return new Ability([
    {
      action: 'read',
      subject: 'Article',
    },
    {
      action: 'update',
      subject: 'Article',
      conditions: { authorId: user.id },
    },
  ]);
};

export default defineAbilitiesFor;

In this example, we define two abilities:

All users can read articles.
Users can only update articles they authored.

Step 3: Integrating CASL with React

To use these abilities in your React components, you can create a context to provide the ability instance throughout your app.

import React, { createContext, useContext } from 'react';
import { Ability } from '@casl/ability';

const AbilityContext = createContext();

export const AbilityProvider = ({ children, user }) => {
  const ability = defineAbilitiesFor(user);

  return (
    <AbilityContext.Provider value={ability}>
      {children}
    </AbilityContext.Provider>
  );
};

export const useAbility = () => useContext(AbilityContext);

Step 4: Protecting Components

Now that you’ve set up the context, you can protect your components using the Can component provided by @casl/react.

import { Can } from '@casl/react';

function Article({ article }) {
  const ability = useAbility();

  return (
    <div>
      <h1>{article.title}</h1>
      <p>{article.content}</p>

      <Can I="update" a="Article">
        <button>Edit Article</button>
      </Can>
    </div>
  );
}

Here, the "Edit Article" button will only be visible if the user has permission to update the article.

Step 5: Handling Unauthorized Access

CASL can also help manage what happens when a user attempts an unauthorized action. This can be done by checking abilities in event handlers or API calls.

const handleEdit = () => {
  if (!ability.can('update', article)) {
    alert('You are not allowed to edit this article!');
    return;
  }

  // proceed with editing logic
};

Conclusion

Integrating CASL with React provides a clean and declarative way to manage authorization in your applications. By defining abilities and using the Can component, you can easily control what users can see and do, improving both the security and user experience of your app.

Integrating CASL with React for Robust Authorization