Benchmark Overview: "immer push vs spread"

This benchmark compares two different methods of adding an item to a list in JavaScript—using the Immer library's produce function versus the spread operator syntax. The main goal is to evaluate their performance in terms of execution speed.

Code Preparation

• Script Preparation Code: This code snippet defines a function createList that generates an array of objects with an id and a value property. The resulting list contains 100 items, and a new nextItem object is created, which will be added to this list during the benchmarking.

• Html Preparation Code: The benchmark uses the Immer library, loaded from a CDN. Immer is designed to enable immutable state management in JavaScript applications by allowing users to work with mutable representations of state that automatically track changes.

Individual Test Cases Explained

1. Immer Approach

   • Benchmark Definition: const updatedList = immer.produce(list, (draft) => { draft.push(nextItem); });
   • Test Name: "immer"
   • Description: This approach uses the Immer library. It creates a draft state where the nextItem is pushed to list. Immer handles the complexity of immutability, allowing developers to write code that appears to mutate state directly while creating immutable updates under the hood.

2. Spread Operator Approach

   • Benchmark Definition: const updatedList = [...list, nextItem];
   • Test Name: "spread"
   • Description: This approach uses the spread operator, which creates a new array by copying all elements from list and appending nextItem. It offers a concise way to maintain immutability, as it creates a copy of the entire array rather than modifying it in place.

Performance Results

The benchmark results indicate a significant difference in execution speed:

• Spread Operator: Achieved 14,294,164 executions per second.
• Immer: Achieved 167,956 executions per second.

Pros and Cons of Both Approaches

Immer Library

Pros:

• Simplifies state management, especially in complex applications.
• Makes it easier to implement immutable data structures without verbose code.

Cons:

• Performance overhead due to the complexity of tracking changes and creating immutable updates.
• Increases bundle size since an additional library is needed.

Spread Operator

Pros:

• Lightweight and built into JavaScript, no external libraries are required.
• Easier to read and understand for those familiar with ES6 syntax.

Cons:

• For very large arrays, copying the entire array to create a new one can be inefficient and expensive in terms of performance.
• Doesn’t handle nested state immutably as seamlessly as Immer.

Other Alternatives

1. Array.prototype.concat(): Similar to the spread operator, it is used to combine arrays without modifying the original array. E.g., const updatedList = list.concat(nextItem);

2. Immutable.js: A library for creating immutable data structures. While it provides performance benefits, it has a steeper learning curve compared to standard JavaScript syntax.

3. Object.assign() with Arrays: This approach can also achieve similar results but is less common and can be less readable.

Conclusion

Overall, the benchmark effectively highlights the trade-offs between utilizing a library like Immer for state management versus leveraging native JavaScript features like the spread operator. Choosing the right approach depends on the specific use case, performance requirements, and the complexity of the state under consideration. For high-performance applications that manage large datasets, the spread operator may often be the preferred choice. For applications that require extensive immutability with complex state changes, Immer can provide significant benefits, albeit with a performance cost.