Benchmark: function dec vs function expr

Tests:

declaration
for (let i = 30000; --i;) { function declaration(arg) { return arg ** 2 } declaration(i) }
expression
for (let i = 30000; --i;) { const expression = function(arg) { return arg ** 2 } expression(i) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
declaration
expression

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; CrOS x86_64 14541.0.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36

Browser/OS: Chrome 132 on Chrome OS 14541.0.0

View result in a separate tab

Test name	Executions per second
declaration	33170.0 Ops/sec
expression	32934.7 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 5 months ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the provided JSON tests the performance differences between two different ways of defining functions in JavaScript: function declarations and function expressions. The benchmark consists of two test cases that repeatedly call the same mathematical operation (squaring a number) using these two methods of function definition in a loop.

### Test Cases Described

1. **Function Declaration**
   ```javascript
   for (let i = 30000; --i;) {
       function declaration(arg) {
           return arg ** 2;
       }
       declaration(i);
   }
   ```
   - **Test Name**: "declaration"
   - **Execution**: This test case uses a function declaration, which is defined before invoking it. Function declarations are hoisted, meaning they can be called anywhere in the scope where they are defined, even before the point of definition in the code.

2. **Function Expression**
   ```javascript
   for (let i = 30000; --i;) {
       const expression = function(arg) {
           return arg ** 2;
       }
       expression(i);
   }
   ```
   - **Test Name**: "expression"
   - **Execution**: This test case uses a function expression, where the function is defined and assigned to a variable before being invoked. Function expressions are not hoisted in the same way as function declarations; they must be defined before they are called.

### Performance Results
The results indicate the number of function executions per second for each method when run in the Chrome 126 browser on a Chrome OS platform.

- **Function Declaration Executions per Second**: ~29071.11
- **Function Expression Executions per Second**: ~28862.20

From these results, we can observe that the function declaration method performed slightly better in this benchmark compared to the function expression method.

### Pros/Cons of Each Approach

#### Function Declarations
- **Pros**:
  - Hoisting allows functions to be called before their definition in the code, which can improve code organization.
  - Clear and concise syntax for defining functions.
- **Cons**:
  - Can lead to confusion in larger scopes where multiple declarations might cause naming conflicts.
  - The hoisting behavior might confuse new developers regarding where and how functions can be invoked.

#### Function Expressions
- **Pros**:
  - More control over when functions are defined and utilized, which can enhance readability.
  - Encourages clearer scoping by defining functions where they are used.
- **Cons**:
  - Not hoisted, which means they must be defined before use, potentially leading to `undefined` function errors if not properly structured.
  - Slightly less performance (as seen in this benchmark), which can matter in high-performance applications.

### Other Considerations
- The differences in performance might not be significant enough in many applications to dictate which approach to use, especially if the functions are not called in a tight loop. The choice may often depend on the specific use case, readability preferences, and maintainability of the codebase.
- Developers might also consider arrow functions (a form of function expression) which offer a more concise syntax and retain the lexical `this` value, enhancing the handling of context in callbacks and methods.

### Alternatives
Other alternatives include:
- **Arrow Functions**: Introduced in ES6, they provide a shorter syntax and can often simplify code by automatically binding `this` to the surrounding context. However, they cannot be used as constructors and do not have their own `this`.
- **Class Methods**: Functions defined within a class can also serve similar purposes and allow for more object-oriented programming techniques.
- **Higher-Order Functions**: Wrapping functions to enhance or modify other functions can also be a viable method depending on the complexity required.

In summary, both function declarations and expressions have their respective pros and cons, and the choice between them may come down to specific use case considerations and coding styles. The benchmarks indicate a slight performance edge for function declarations in this specific testing scenario.

Related benchmarks:

function dec vs function expr (version: 1)

Comparing performance of: declaration vs expression

Created: 5 months ago by: Guest

Jump to the latest result

declaration

expression

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 5 months ago):