In many applications, having the ability to undo and redo actions is a crucial feature. With Immer, a powerful state management library, you can easily add undo functionality to your Svelte applications. In this blog post, we’ll explore the steps to implement undo functionality using Immer.

Setting up the project

First, let’s set up a new Svelte project. Open your terminal and run the following commands:

npx degit sveltejs/template svelte-immer-undo
cd svelte-immer-undo
npm install

Installing Immer

Next, let’s install Immer by running the following command in your project directory:

npm install immer

Adding undo functionality

To implement undo functionality, we’ll use Immer’s produce function to create a draft of our state and track the history of actions applied to it. Here’s an example implementation for a simple counter component:

// Counter.svelte
<script>
  import { produce } from 'immer';
  import { writable, get } from 'svelte/store';

  const initialState = { count: 0 };
  const undoHistory = [];
  const redoHistory = [];

  export let count = writable(initialState.count);

  function increment() {
    const currentState = get(count);

    // Create a draft of the state and apply the increment action
    const nextState = produce(currentState, draft => {
      draft.count += 1;
    });

    // Push the current state to the undo history
    undoHistory.push(currentState);

    // Update the count store with the new state
    count.set(nextState);
  }

  function undo() {
    if (undoHistory.length > 0) {
      const previousState = undoHistory.pop();

      // Push the current state to the redo history
      redoHistory.push(get(count));

      // Set the count store to the previous state
      count.set(previousState);
    }
  }

  function redo() {
    if (redoHistory.length > 0) {
      const nextState = redoHistory.pop();

      // Push the current state to the undo history
      undoHistory.push(get(count));

      // Set the count store to the next state
      count.set(nextState);
    }
  }
</script>

<button on:click={increment}>Increment</button>
<p>Count: {$count}</p>
<button on:click={undo}>Undo</button>
<button on:click={redo}>Redo</button>

In the example above, we use Svelte’s writable store to manage the state and keep track of the history of actions. The undo function pops the last state from the undo history and sets it as the current state, while the redo function does the opposite, allowing us to redo previously undone actions.

Summary

Adding undo functionality to your Svelte applications can greatly enhance the user experience. With Immer’s powerful produce function, managing state and tracking action history becomes a breeze. By following the steps outlined in this blog post, you can easily implement undo functionality in your Svelte applications using Immer.

Give it a try and elevate your application to the next level!

#sveltejs #Immer #state-management #undo-functionality