Benchmark: Plain object, for vs for in vs for of vs while

Script Preparation code:

var a = {
    first: 'john',
    last: 'smith',
    address: {
        street: 'street street'
    }
};

var b = {
    first: 'j',
    last: 's'
};

Tests:

for loop
const props = Object.keys(a); const length = props.length; let hasNewKey = false; for (let i = 0; i < length; i++) { const key = props[i]; if (!(key in b)) { hasNewkey = true; } }
for of
const props = Object.keys(a); let hasNewKey = false; for (const key of props) { if (!(key in b)) { hasNewkey = true; } }
for in
let hasNewKey = false; for (const key in a) { if (!(key in b)) { hasNewkey = true; } }
while
let hasNewKey = false; const props = Object.keys(a); let key, i = 0; while (key = props[i++]) { if (!(key in b)) { hasNewKey = true; } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for loop
for of
for in
while

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 its test cases.

**Benchmark Definition**

The benchmark measures how different JavaScript loops compare in terms of performance when iterating over an object's keys. The object `a` contains nested properties, including a nested object `address`.

**Options Compared**

There are four options compared:

1. **For loop**: A traditional for loop that uses the `for` keyword to iterate over the keys.
2. **For of loop**: A newer feature introduced in ECMAScript 2015 (ES6), which allows iterating over iterable values, including objects, using the `for...of` syntax.
3. **For in loop**: An older way of iterating over an object's properties using the `in` keyword.
4. **While loop**: A traditional while loop that uses a condition to iterate until it's false.

**Pros and Cons**

Here are some general pros and cons of each approach:

* **For loop**: Pros - easy to read, understand, and maintain; Cons - can be slower due to the overhead of checking the loop condition. This method is also less efficient when dealing with large datasets.
* **For of loop**: Pros - more concise and expressive than traditional for loops; Cons - may have performance issues if not optimized correctly. This method is well-suited for modern JavaScript development, but can be slower than other methods due to its syntax overhead.
* **For in loop**: Pros - simple and easy to understand; Cons - can be slower and less efficient than other methods due to the way it iterates over properties. This method is generally used when you need to iterate over an object's own properties, but not necessarily its keys.
* **While loop**: Pros - can provide more control over iteration, especially for complex logic; Cons - can be harder to read and maintain, as well as slower due to the condition check.

**Library Usage**

None of the test cases use any libraries beyond JavaScript itself. However, it's worth noting that some optimizations might require using external libraries or third-party functions.

**Special JS Features**

There are no special JavaScript features used in this benchmark beyond what's required by each loop syntax (e.g., `for...of`, `in`).

**Alternatives**

Some alternative approaches to iterating over an object's keys could include:

* Using `Object.keys()` and indexing into the resulting array
* Using a `forEach` loop with an arrow function
* Using a recursive function to iterate over nested properties
* Using a third-party library like Lodash or Ramda for iteration and filtering

Keep in mind that these alternatives may have different performance characteristics, readability, and maintainability trade-offs compared to the original four loop options.

Related benchmarks:

Plain object, for vs for in vs for of vs while (version: 0)

compare different ways to loop the keys of an object

Comparing performance of: for loop vs for of vs for in vs while

Created: 3 years ago by: Guest

Jump to the latest result

for loop

for of

for in

while

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):