Benchmark: Foreach vs Spread

Tests:

Foreach
var a = new Map(); a.set("a", 12345); a.set("b", 45678); a.set("c", 13579); a.set("d", 24680); a.set("e", 09876); a.set("f", 54321); a.set("g", 12121); a.set("h", 23232); a.set("i", 45454); var b = []; a.forEach((c) => b.push(c));
Spread
var a = new Map(); a.set("a", 12345); a.set("b", 45678); a.set("c", 13579); a.set("d", 24680); a.set("e", 09876); a.set("f", 54321); a.set("g", 12121); a.set("h", 23232); a.set("i", 45454); var b = []; b = [...b, ...a ];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Foreach
Spread

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Foreach	4238518.5 Ops/sec
Spread	4733764.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the benchmark.

**What is being tested?**

The provided benchmark measures the performance of two approaches when iterating over an array of objects using `Map` and `Array`.

In the first approach, "Foreach", the code uses the `forEach()` method to iterate over the keys of the `Map` object, and pushes each key into an array (`b`). This is done in a specific order: `a.forEach((c) => b.push(c));`

In the second approach, "Spread", the code uses the spread operator (`...`) to create a new array that includes all elements from another array (`b`) and then spreads its own elements (keys of the `Map` object `a`). This is done as follows: `var b = []; b = [...b, ...a];`

**Options being compared**

Two options are being compared:

1. **Foreach**: Using `forEach()` method to iterate over the keys of a `Map` object.
2. **Spread**: Using the spread operator (`...`) to create a new array that includes all elements from another array and then spreads its own elements.

**Pros and Cons of each approach**

*   **Foreach Approach:**
    *   Pros:
        *   Easy to read and understand, as it iterates over the keys in a straightforward manner.
        *   Can be used when you need to perform an operation on each key in the `Map`.
    *   Cons:
        *   May incur additional overhead due to the call stack management of the `forEach()` method.
*   **Spread Approach:**
    *   Pros:
        *   More concise and potentially faster, as it avoids the overhead of the `forEach()` method and creates a new array all at once.
        *   Can be used when you need to perform an operation on each element in the original array (`a`).
    *   Cons:
        *   Less readable than the foreach approach, as the spread operator is not immediately intuitive for iterating over objects.

**Other Considerations**

*   The benchmark assumes that the `Map` object's keys are not too large or complex to be pushed into an array. If you need to handle larger values, you may want to consider using a more optimized data structure.
*   The performance difference between these two approaches can depend on various factors such as JavaScript engine optimizations, array and map sizes, and device configurations.

**Library used**

The `Map` object is a built-in JavaScript object that stores key-value pairs. Its primary purpose is to provide an efficient way of storing and retrieving data by using keys for lookup.

**Special JS feature or syntax**

This benchmark uses the spread operator (`...`), which was introduced in ECMAScript 2015 (ES6). The spread operator allows you to expand array or object elements into a new array or object. In this benchmark, it's used to create a new array that includes all elements from `b` and then spreads its own elements.

**Alternatives**

If you're looking for alternatives to these approaches, here are a few:

*   For iterating over an array of objects when performance is critical:
    *   Using a `for...in` loop instead of `forEach()`, as it avoids the overhead of the call stack management.
*   For creating a new array from an existing one with additional elements:
    *   Using other methods like `concat()`, `push()` along with some creative use of spread operator or even manual iteration.

Overall, this benchmark provides valuable insights into how different approaches can impact performance when working with `Map` objects and arrays in JavaScript.

Related benchmarks:

Foreach vs Spread (version: 0)

Comparing performance of: Foreach vs Spread

Created: 6 years ago by: Guest

Jump to the latest result

Foreach

Spread

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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