Benchmark: Iterator with Array#pop() vs iterator with Array#shift()

Tests:

Array#pop()
const objPop = { a: 1, b: 2, c: 3, [Symbol.iterator]() { const elements = Object.entries( this ).reverse(); // 1 let index = elements.length - 1; return { next() { if ( index >= 0 ) { index--; const [ k, v ] = elements.pop(); // 2 return { value: { k, v }, done: false }; } return { value: undefined, done: true }; } } } }; let i = 0; while ( i++ < 10000 ) { [ ...objPop ]; }
Array#shift()
const objShift = { a: 1, b: 2, c: 3, [Symbol.iterator]() { const elements = Object.entries( this ); return { next() { if ( elements.length > 0 ) { const [ k, v ] = elements.shift(); return { value: { k, v }, done: false }; } return { value: undefined, done: true }; } } } }; let i = 0; while ( i++ < 10000 ) { [ ...objShift ]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array#pop()
Array#shift()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.3 Safari/605.1.15

Browser/OS: Safari 15 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Array#pop()	107.6 Ops/sec
Array#shift()	93.9 Ops/sec

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

LLMs can make mistakes. Check important info.

Measuring the performance of different approaches to iterating over an array using `Array#pop()` and `Array#shift()` is crucial for optimizing code that manipulates arrays.

**What's being tested:**

In this benchmark, two test cases are compared:

1. Using `Array#pop()`: This approach creates an iterator that reverses the object's entries (using `Object.entries()`) and then pops elements from the reversed array until it reaches the end.
2. Using `Array#shift()`: This approach creates an iterator that iterates over the object's entries and shifts each element off the front of the array.

**Options compared:**

The benchmark compares two different approaches:

1. **Reverse iteration with `pop()`**: The iterator is created by reversing the object's entries, which results in a reversed array. Then, elements are popped from this reversed array until it reaches the end.
2. **Iteration with `shift()`**: The iterator directly iterates over the object's entries and shifts each element off the front of the array.

**Pros and cons:**

1. **Reverse iteration with `pop()`**:
	* Pros: This approach can be more efficient if the object has a large number of elements, as it allows for early termination when the reversed array reaches its end.
	* Cons: Reversing the array requires additional memory allocation and copying, which can lead to higher overhead for small arrays or objects with many entries.
2. **Iteration with `shift()`**:
	* Pros: This approach has lower overhead since it only needs to iterate over the original object's entries without reversing the array.
	* Cons: If the iterator reaches the end of the array, additional work is required to return undefined, which can lead to slightly higher overhead.

**Library considerations:**

In both test cases, `Object.entries()` is used to create an array of key-value pairs from the object. This function is a built-in JavaScript method that returns an array of tuples containing each entry's key and value.

**Special JavaScript features:**

1. **Symbol.iterator**: Both test cases use the `Symbol.iterator` property to create an iterator for the array.
2. **Array#push()` / `Array#pop()`: These methods are used in the script preparation code to push elements onto the array or pop them off, respectively.

**Alternative approaches:**

Other alternatives could be explored:

1. Using a `Set` instead of an array to store unique values, which can provide faster lookup and removal times.
2. Implementing a custom iterator using `for...of` loops and manual indexing, which can provide more control over the iteration process.
3. Using `Array.prototype.forEach()` or `Array.prototype.map()` with a callback function to iterate over the array.

However, these alternatives may not be as efficient or readable as the tested approaches, and their performance characteristics may vary depending on the specific use case.

Related benchmarks:

Iterator with Array#pop() vs iterator with Array#shift() (version: 0)

Comparing performance of: Array#pop() vs Array#shift()

Created: 2 years ago by: Guest

Jump to the latest result

Array#pop()

Array#shift()

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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