Benchmark: Array spread vs. object mutate when using Object.assign

Script Preparation code:

var state = {}
var cols = [{id: 1, key: 'value'}, {id: 2, key: 'value'}]
for (var i = 0; i < 2000; i++) {
    state[i] = {
        id: i,
        key: 'value'
    };
};

Tests:

Spread
const colDefs = cols.map(c => {return {[c.id]: c}}); const test = Object.assign({}, state, ...colDefs);
Mutate
const colDefs = {} cols.forEach(c => { colDefs[c.id] = c; }); const test = Object.assign({}, state, colDefs);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
Mutate

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

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Let's break down the benchmark and explain what is being tested, along with the pros and cons of each approach.

**Benchmark Definition**

The benchmark measures the performance difference between two approaches when assigning new values to an object using `Object.assign()`. The test case uses Redux state, but this is not relevant to the core algorithm being compared.

**Approaches Compared:**

1. **Spread Approach**: This method uses the spread operator (`...`) to create a new array of objects and then assigns it to the original object using `Object.assign()`.
2. **Mutate Approach**: This method modifies the original object by assigning its properties directly into the object, creating a shallow copy.

**Pros and Cons:**

**Spread Approach:**

Pros:

* More readable and maintainable code
* Creates a new array of objects, which can be beneficial for caching or other optimizations
* Less prone to errors when dealing with nested objects

Cons:

* May incur additional overhead due to the creation of a new array
* Can be slower if the resulting array is very large

**Mutate Approach:**

Pros:

* Generally faster than the spread approach, as it avoids creating an intermediate array
* Can be more efficient for very large datasets

Cons:

* Less readable and maintainable code
* Can lead to errors when dealing with nested objects or unexpected property names
* May cause issues if the original object is modified concurrently

**Library:**

The benchmark uses `Object.assign()`, which is a built-in JavaScript method that creates a shallow copy of an object.

**Special JS Feature/Syntax:**

There are no special features or syntax used in this benchmark. The focus is on comparing two different approaches to assigning values to an object.

**Other Alternatives:**

If you need to assign new values to an object, other alternatives include:

* Using a library like Lodash's `assignIn()` method
* Using a custom implementation of shallow copy using loops or recursion
* Using a data structure like a Map or an Object with the same properties as the original object

Keep in mind that the choice of approach depends on the specific use case and requirements. The spread approach is generally recommended for its readability and maintainability, while the mutate approach may be preferred for performance-critical applications.

Related benchmarks:

Array spread vs. object mutate when using Object.assign (version: 0)

Evaluation of array spread vs. object mutate when assigning new values to redux state

Comparing performance of: Spread vs Mutate

Created: 5 years ago by: Guest

Jump to the latest result

Spread

Mutate

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):