Benchmark: Copying data; mapping vs. spreading then modifying vs. Object.assign then modifiying

Script Preparation code:

var data = [{
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    }
];

Tests:

Mapping
data.map((d, i) => i=== 2 ? "replaced" : d)
spreading, then modifying
const copy = [...data]; copy[2] = "replaced";
Object.assign, then modifying
const copy = Object.assign([], data) copy[2] = "replaced";

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Mapping
spreading, then modifying
Object.assign, then modifying

Fastest: N/A

Slowest: N/A

Latest run results:

No previous 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 provided JSON to understand what is being tested on MeasureThat.net.

**Benchmark Definition**
The benchmark measures how different approaches compare when copying and modifying data in JavaScript. The main tasks are:

1. Mapping: This involves using the `map()` method to create a new array with modified values.
2. Spreading, then modifying: This approach uses the spread operator (`...`) to create a copy of the original array, modifies it by assigning a new value to an index, and then assigns another value to that index.
3. Object.assign, then modifying: This approach uses the `Object.assign()` method to create a shallow copy of the original object (in this case, an array), modifies it by assigning a new value to an index, and then assigns another value to that index.

**Options Compared**
The benchmark compares three different approaches:

1. **Mapping**: Using the `map()` method to create a new array with modified values.
2. **Spreading, then modifying**: Using the spread operator (`...`) to create a copy of the original array, modifying it by assigning a new value to an index, and then assigning another value to that index.
3. **Object.assign, then modifying**: Using the `Object.assign()` method to create a shallow copy of the original object (in this case, an array), modifying it by assigning a new value to an index, and then assigning another value to that index.

**Pros and Cons of Each Approach**

1. **Mapping**:
	* Pros: Can be more concise and readable when dealing with simple transformations.
	* Cons: Creates a new array, which can be memory-intensive for large datasets.
2. **Spreading, then modifying**:
	* Pros: Allows for more control over the data being copied and modified.
	* Cons: Requires additional operations (spreading and assigning values), making it potentially slower than other approaches.
3. **Object.assign, then modifying**:
	* Pros: Can be faster than mapping or spreading, as it avoids creating a new array.
	* Cons: May not work correctly with nested objects or arrays, as only shallow copies are made.

**Library and Syntax Used**
In the provided benchmark, no libraries are explicitly mentioned. However, it's worth noting that some of these approaches rely on internal methods in JavaScript objects (e.g., `map()`, `Object.assign()`). While not technically a library, these built-in methods can have varying performance characteristics depending on the browser and engine being used.

**Special JS Feature or Syntax**
The provided benchmark does not explicitly use any special JavaScript features or syntax. However, it's worth noting that some browsers may optimize certain aspects of these approaches differently due to their implementation (e.g., how they handle array copying).

**Other Alternatives**

While not mentioned in the benchmark definition, other approaches could be used for similar tasks:

1. Using `forEach()` instead of `map()`.
2. Using `reduce()` instead of `map()`.
3. Utilizing libraries like Lodash or Ramda for more complex transformations.
4. Leveraging browser-specific optimizations (e.g., `Array.prototype.slice()` or `Array.prototype.concat()`).

Keep in mind that these alternatives may have different trade-offs in terms of performance, readability, and memory usage compared to the approaches tested in the benchmark.

Related benchmarks:

Copying data; mapping vs. spreading then modifying vs. Object.assign then modifiying (version: 0)

Comparing performance of: Mapping vs spreading, then modifying vs Object.assign, then modifying

Created: 3 years ago by: Guest

Jump to the latest result

Mapping

spreading, then modifying

Object.assign, then modifying

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):