Benchmark: object keys vs loop

Script Preparation code:

var a = [{"id":7,"h":76},{"id":4,"h":34},{"id":9,"h":89}];
var d = [];

Tests:

fori
for(var i=0;i<a.length;i++)d.push(a[i].id);
forin
for(var i in a)d.push(i.id);
foreach
b.forEach((i)=>d.push(i.id));
backwhile
var i = a.length; while(--i)d.push(a[i].id);
cache4
var z = a.length; for(var i=0;i<z;i++)d.push(a[i].id);
4of
for(var i of a)d.push(i.id);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
fori
forin
foreach
backwhile
cache4
4of

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):

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmark created on MeasureThat.net. This benchmark compares the performance of six different approaches to access and iterate over an array of objects.

**Approaches Compared:**

1. **For loop with index variable (`for(var i=0;i<a.length;i++)d.push(a[i].id);`): This approach uses a traditional `for` loop with an index variable, which is the most common way to iterate over an array in JavaScript.
2. **For...in loop (`for(var i in a)d.push(i.id);`): This approach uses the `for...in` loop, which iterates over the properties of an object (in this case, the keys of the array).
3. **ForEach loop with callback function (`b.forEach((i)=>d.push(i.id));`): This approach uses the `forEach` method, which is a more modern way to iterate over arrays.
4. **While loop with decrementing index variable (`var i = a.length;\r\nwhile(--i)d.push(a[i].id);`): This approach uses a `while` loop with an index variable that decrements on each iteration.
5. **For...of loop (`for(var i of a)d.push(i.id);`): This approach uses the `for...of` loop, which is a more modern way to iterate over arrays (similar to `forEach`, but without the need for a callback function).
6. **Cache iteration with variable index (`var z = a.length;\r\nfor(var i=0;i<z;i++)d.push(a[i].id);`): This approach uses a cached value of the array length and iterates over it using a traditional `for` loop.

**Pros and Cons:**

* **For loop with index variable:** Pros - simple, efficient, and widely supported. Cons - can be error-prone if the indexing is off.
* **For...in loop:** Pros - easy to implement, but may have issues with object prototypes and duplicate keys. Cons - slower than traditional `for` loops due to the overhead of iterating over properties.
* **ForEach loop with callback function:** Pros - modern, efficient, and concise. Cons - requires a callback function, which can be error-prone if not implemented correctly.
* **While loop with decrementing index variable:** Pros - efficient, but may have issues with index overflow or underflow.
* **For...of loop:** Pros - modern, efficient, and concise. Cons - only available in ECMAScript 2015 and later versions.
* **Cache iteration with variable index:** Pros - simple, efficient, but may have issues with indexing if the cached value is incorrect.

**Library and Special JS Features:**

None of the libraries are explicitly mentioned in the provided JSON. However, the `forEach` loop uses a method that relies on the Array.prototype object, which is part of the JavaScript standard library.

No special JavaScript features are used in this benchmark. The tests only use basic JavaScript syntax and semantics.

**Other Alternatives:**

There are other approaches to iterate over arrays in JavaScript, such as using `Array.prototype.map()`, `Array.prototype.filter()`, or using a traditional `for` loop with an index variable (e.g., `for(var i=0;i<a.length;i++)d.push(a[i].id);`). These alternatives may have different performance characteristics and trade-offs compared to the approaches tested in this benchmark.

Overall, the choice of iteration approach depends on personal preference, performance requirements, and the specific use case. The MeasureThat.net benchmark provides a convenient way to compare the performance of different approaches and choose the most efficient one for your needs.

Related benchmarks:

object keys vs loop (version: 0)

Comparing performance of: fori vs forin vs foreach vs backwhile vs cache4 vs 4of

Created: 9 years ago by: Guest

Jump to the latest result

fori

forin

foreach

backwhile

cache4

4of

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):