Benchmark: Eval vs new Function (when both return a function)

Script Preparation code:

var evalFunc = eval('(function(){ return () => 2 * 3; })();'); 
var newFunc = new Function('return 2 * 3');
var predefinedFunc = () => 2 * 3;

Tests:

eval
evalFunc();
new Func
newFunc();
predefined Func
predefinedFunc();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
eval
new Func
predefined Func

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model gemma2:9b, generated one year ago):

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This benchmark compares the performance of three different ways to create a function in JavaScript:

* **`eval()`:** Executes a string as JavaScript code. In this case, it executes a string that defines an anonymous function returning the result of 2 * 3.

* **`new Function()`:**  Constructs a new function object from a string. Similar to `eval()`, it's given a string defining a function returning 2 * 3.

* **Predefined Function:** This approach simply defines the function directly using arrow function syntax: `() => 2 * 3`.

**Pros and Cons:**

* **`eval()`**:
    * **Pro:** Can be convenient for dynamically creating functions from user input or other sources.
    * **Con:**  Significant performance overhead compared to direct function definition. It's also a security risk if the string passed to `eval()` comes from untrusted sources, as it can execute arbitrary code.

* **`new Function()`**: 
    * **Pro:** Similar to `eval()`, allows for dynamic function creation.
    * **Con:** Also suffers from performance issues and carries similar security risks as `eval()`. It's generally considered less performant than `eval()` in most cases.

* **Predefined Function:**
    * **Pro:**  Most performant option due to direct definition. No runtime overhead associated with parsing or executing code strings.
    * **Con:** Requires the function to be defined beforehand, limiting its flexibility compared to `eval()` and `new Function()`.

**Alternatives:**

* **Template Literals (for string interpolation):** If you need to construct strings dynamically, template literals are a safer and more efficient alternative to `eval()`. 
* **Function Constructors:** While not used in this benchmark, function constructors provide another way to create functions dynamically. They can sometimes be slightly faster than `new Function()` but are still generally less performant than direct function definition.

**Key Takeaway:** When performance is crucial, avoid using `eval()` and `new Function()`.  Directly defining your functions (using arrow functions or regular function declarations) is the most efficient approach in almost all cases.

Related benchmarks:

Eval vs new Function (when both return a function) (version: 3)

Comparing performance of: eval vs new Func vs predefined Func

Created: 4 years ago by: Registered User

Jump to the latest result

eval

new Func

predefined Func

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model gemma2:9b, generated one year ago):