Benchmark: for in break vs object keys smaller

Script Preparation code:

var testObj = {}
for (let i = 0; i < 100; i++) {
  const randomString = Math.random().toString(36).substr(2, 5);
  testObj[randomString] = randomString;
}

Tests:

for in break
let output; for (const key in testObj) { output = testObj[key]; console.log(output); break; }
Object keys
let output; output = Object.values(testObj)[0]; console.log(output);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for in break
Object keys

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 provided JSON and benchmark preparation code to understand what's being tested.

**Benchmark Definition:**
The benchmark definition is a JavaScript script that creates an object `testObj` with 100 random strings as keys and values. The script then tests two different approaches to accessing and logging the value of one of these randomly generated strings.

**Script Preparation Code:**
```javascript
var testObj = {};
for (let i = 0; i < 100; i++) {
  const randomString = Math.random().toString(36).substr(2, 5);
  testObj[randomString] = randomString;
}
```
This code creates an object `testObj` with 100 properties, where each property has a string value.

**Html Preparation Code:**
There is no HTML preparation code provided in this benchmark definition.

Now, let's examine the individual test cases:

**Test Case 1: "for in break"**

```javascript
let output;
for (const key in testObj) {
  output = testObj[key];
  console.log(output);
  break;
}
```
This test case uses the `for...in` loop to iterate over the object's properties. When a property is found, its value is assigned to the `output` variable and logged to the console using `console.log`. The `break` statement exits the loop immediately after the first iteration.

**Test Case 2: "Object keys"**

```javascript
let output;
output = Object.values(testObj)[0];
console.log(output);
```
This test case uses the `Object.values()` method to get an array of the object's values. The `[0]` index is used to access the first element of this array, which corresponds to one of the randomly generated string values.

**Comparison:**

* **For-in loop vs Object.keys()**: Both approaches aim to log a single value from `testObj`. However, the for-in loop has a few advantages:
	+ It's more efficient because it only needs to iterate over the object's properties once.
	+ It provides additional information about the property being iterated (its name and whether it's an own property of the object).
* **Object.keys() vs direct indexing**: Using `Object.values()` followed by `[0]` is a more modern and concise way to access a single value from an array. However, direct indexing might be slightly faster because it avoids the overhead of calling a method.

**Pros and Cons:**

* For-in loop:
	+ Pros: Efficient, provides additional information about properties.
	+ Cons: May not work as expected if the object has prototype chains or inherited properties.
* Object.keys() vs direct indexing:
	+ Pros: Modern and concise, avoids potential issues with property names.
	+ Cons: Might be slightly slower due to method call overhead.

**Library/Languages Features Used:**

* None are explicitly mentioned in this benchmark definition. However, it's worth noting that `Object.values()` is a relatively modern feature introduced in ECMAScript 2019.

**Special JS Features/ Syntax Used:**
None are explicitly mentioned in this benchmark definition.

**Alternatives:**

Other ways to access and log a single value from an object might include:

* Using the bracket notation (`testObj['randomString']`)
* Using the `in` operator with a string key (`'randomString' in testObj`)
* Using the spread operator (`[...Object.values(testObj)][0]`)

Related benchmarks:

for in break vs object keys smaller (version: 0)

Comparing performance of: for in break vs Object keys

Created: 5 years ago by: Guest

Jump to the latest result

for in break

Object keys

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):