Benchmark: Object.entries VS Object.keys VS Object.keys with extra array VS Object.entries without array 3

Script Preparation code:

function makeid() {
  var text = "";
  var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

  for (var i = 0; i < 5; i++)
    text += possible.charAt(Math.floor(Math.random() * possible.length));

  return text;
}

window.parentObj = {};

for (let i = 0; i < 100; i++) {
	window.parentObj[makeid()] = makeid();
}

Tests:

Object.entries
const newObj = {}; Object.entries(window.parentObj).forEach(([k, v], i) => { if ((i % 2) === 0) { newObj[k] = v; } });
Object.entries.for
const newObj = {}; for (const [k, v] of Object.entries(window.parentObj)) { if ((i % 2) === 0) { newObj[k] = v; } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.entries
Object.entries.for

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark and its test cases to explain what's being tested, compared, and their pros and cons.

**Benchmark Definition JSON**

The benchmark is testing three approaches for iterating over an object in JavaScript:

1. `Object.entries()`
2. `for...of` loop with `Object.entries()`
3. `Object.keys()` without the array syntax (i.e., using `Object.keys()` as if it returns an array of keys)

**Test Cases**

The test cases are individual benchmarks for each of the three approaches:

1. **Object.entries**
	* The benchmark preparation code creates a large object with 100 properties, where each property value is another random string.
	* The benchmarking code uses `Object.entries()` to iterate over the object and add only every other entry to a new object (`newObj`).
2. **Object.entries.for**
	* This test case is identical to the first one, but uses a `for...of` loop with `Object.entries()` to iterate over the object.
3. **Object.keys() without array syntax**
	* In this test case, `Object.keys()` is used as if it returns an array of keys, instead of the actual key-value pairs returned by the method.

**Comparison**

The benchmark is comparing the performance of these three approaches:

1. `Object.entries()`: This approach uses the spread operator (`...`) to unpack the key-value pairs into separate variables.
2. `for...of` loop with `Object.entries()`: This approach uses a traditional `for` loop with the `Object.entries()` method as its iteration source.
3. `Object.keys()` without array syntax: This approach attempts to use `Object.keys()` as if it returns an array of keys, which is not how the method works.

**Pros and Cons**

Here's a brief summary of each approach:

1. **`Object.entries()`:**
	* Pros: More concise and expressive way to iterate over objects.
	* Cons: May have performance overhead due to the spread operator and destructuring assignment.
2. **`for...of` loop with `Object.entries()`**: 
	* Pros: More control over iteration and can be more efficient for large datasets.
	* Cons: Less concise than using `Object.entries()`.
3. **`Object.keys()` without array syntax:** 
	* Pros: None, as this approach is incorrect and may cause errors or unexpected behavior.
	* Cons: This approach will likely perform poorly due to the incorrect usage of `Object.keys()`.

**Library and Special JS Feature**

There are no external libraries used in these benchmarks. However, it's worth noting that some modern JavaScript features, such as async/await and generators, are not being used in this benchmark.

The only special syntax used is the spread operator (`...`) in the `Object.entries()` approach, which is a modern JavaScript feature introduced in ECMAScript 2015 (ES6).

**Alternatives**

Some alternative approaches to iterating over objects in JavaScript include:

1. Using a traditional `for` loop with `in` keyword: `for (key in obj) { ... }`
2. Using a `forEach()` method or `map()` function: `obj.forEach((value, key) => { ... });`
3. Using a library like Lodash's `keys()` function: `_keys(obj)`

Keep in mind that the choice of iteration approach depends on the specific use case and performance requirements.

I hope this explanation helps!

Related benchmarks:

Object.entries VS Object.keys VS Object.keys with extra array VS Object.entries without array 3 (version: 0)

Comparing performance of: Object.entries vs Object.entries.for

Created: 4 years ago by: Guest

Jump to the latest result

Object.entries

Object.entries.for

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):