Benchmark: function vs class with external declarations

Script Preparation code:

var arr = 1
var functionExpression = function(item) {
  arr  = item
};
function functionDeclaration(item) {
  arr  = item
}
class Test {
  constructor() {  }
  addItem(item){
      arr  = item
  }
}
var _test = new Test()

function functionClass(item) {
  _test.addItem(item);
}

Tests:

function declaration
arr =2 for (let i = 1; i < 10000; i++) { functionDeclaration(i); }
function expression
arr =1 for (let i = 1; i < 10000; i++) { functionExpression(i); }
class
arr =1 for (let i = 1; i < 10000; i++) { _test.addItem(i); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
function declaration
function expression
class

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36 Edg/132.0.0.0

Browser/OS: Chrome 132 on Windows

View result in a separate tab

Test name	Executions per second
function declaration	79686.0 Ops/sec
function expression	79841.1 Ops/sec
class	79922.6 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 3 months ago):

LLMs can make mistakes. Check important info.

This benchmark compares the performance of three different approaches to performing an assignment operation using JavaScript: function declarations, function expressions, and class methods. Let's break down each approach, noting the pros and cons, and discuss considerations regarding their performance.

### Benchmark Overview

1. **Function Declaration**:
   - **Test Definition**: 
     ```javascript
     arr = 2
     for (let i = 1; i < 10000; i++) {
         functionDeclaration(i);
     }
     ```
   - **Description**: This test uses a traditional function declaration to assign values to a variable. Function declarations are defined using the `function` keyword.

2. **Function Expression**:
   - **Test Definition**: 
     ```javascript
     arr = 1
     for (let i = 1; i < 10000; i++) {
         functionExpression(i);
     }
     ```
   - **Description**: This test uses a function expression, which is defined by assigning an anonymous function to a variable, allowing the function to be called by that variable's name.

3. **Class Method**:
   - **Test Definition**: 
     ```javascript
     arr = 1
     for (let i = 1; i < 10000; i++) {
         _test.addItem(i);
     }
     ```
   - **Description**: This test uses a method defined within a JavaScript class. The `addItem` method manipulates the variable `arr` through a class instance `_test`.

### Performance Results
In the benchmark results for a specific test environment (Safari 18):

- **Class**: 314,659.59 executions per second
- **Function Expression**: 312,349.50 executions per second
- **Function Declaration**: 312,081.38 executions per second

### Performance Analysis
- **Class** seems to perform slightly better than both function declaration and function expression in this instance. 
  - **Pros**:
    - Classes provide a clear structure for objects and methods, which can enhance code organization and reusability.
    - They also allow the use of inheritance, which can lead to enhanced maintainability in larger applications.
  - **Cons**:
    - Classes can introduce some overhead due to the context of `this` that must be managed, especially when not using arrow functions.

- **Function Declaration**:
  - **Pros**:
    - Hoisted, meaning they can be called before their definition in the code.
    - They are cleaner and more straightforward for simple tasks and can improve readability.
  - **Cons**:
    - Typically less flexible for callbacks or functional programming patterns compared to expressions.

- **Function Expression**:
  - **Pros**:
    - Not hoisted, so they encourage a top-down execution style. This can result in fewer issues with undeclared usage.
    - They can be assigned as callbacks, enhancing functional programming capabilities.
  - **Cons**:
    - Less intuitive when declaring functions that might be reused in multiple contexts.

### Other Considerations
- **Execution Environment**: Performance can vary significantly in different environments (e.g., browsers, Node.js). JavaScript engines (like V8 for Chrome and SpiderMonkey for Firefox) can optimize code uniquely, affecting execution speed.
  
- **Scalability**: While these comparisons provide insights into execution speed, it's crucial to weigh the performance advantages against clarity and maintainability. Code that is easy to understand is generally more sustainable.

### Alternatives
- **Arrow Functions**: Can be used in place of traditional functions as expressions. They provide a concise syntax and lexical scoping of `this`, although they cannot be used as constructors.
- **Async Functions**: For asynchronous programming, functions can also be wrapped in `async` to support `await`, providing a different paradigm for executing code which might involve I/O operations.
- **Performance Optimizations**: Depending on the browsers and the specific use-case, developers might need to hand-tune performance-critical code using web workers, or native add-ons, or offload intensive tasks to backend services.
  
Ultimately, the choice between these options should consider not only performance metrics but also factors such as code readability, maintainability, and future-proofing against evolving JavaScript standards.

Related benchmarks:

function vs class with external declarations (version: 1)

Comparing performance of: function declaration vs function expression vs class

Created: 3 months ago by: Guest

Jump to the latest result

function declaration

function expression

class

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 3 months ago):