Benchmark: typeof vs instanceof

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

var valueToCheck = {
  foo: '',
  bar: 42,
  baz: false,
};

Tests:

typeof
console.log(typeof valueToCheck === 'object');
instanceof
console.log(valueToCheck instanceof Object);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof
instanceof

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:145.0) Gecko/20100101 Firefox/145.0

Browser/OS: Firefox 145 on Linux

View result in a separate tab

Test name	Executions per second
typeof	81200.4 Ops/sec
instanceof	102393.8 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 11 months ago):

LLMs can make mistakes. Check important info.

The benchmark you provided compares two JavaScript approaches for checking if a variable is an object: using `typeof` and using `instanceof`. The primary goal of this benchmark is to measure the performance difference between these two methods when applied to an object.

### Description of Options Compared

1. **`typeof` Operator**:
   - **Benchmark Definition**: `console.log(typeof valueToCheck === 'object');`
   - **Test Name**: `typeof`
   - The `typeof` operator checks the variable's type and returns a string. Specifically, it checks whether `valueToCheck` is of the type "object". It will return "object" for objects, arrays, and `null`, which is a known quirk of JavaScript.

2. **`instanceof` Operator**:
   - **Benchmark Definition**: `console.log(valueToCheck instanceof Object);`
   - **Test Name**: `instanceof`
   - The `instanceof` operator checks the prototype chain of the variable to determine if it is an instance of a specific constructor (in this case, `Object`). It returns `true` if `valueToCheck` is derived from `Object`, even if it is a more specific object type (like an array or a function).

### Pros and Cons

- **`typeof`**:
  - **Pros**:
    - Simplicity: Easy to use and understand.
    - Directly returns the type as a string.
  - **Cons**:
    - Quirks: Will return "object" for arrays and for `null`, making it less precise for distinguishing between different object types.
  
- **`instanceof`**:
  - **Pros**:
    - Accuracy: Accurately checks if an object is an instance of a specific constructor, allowing more precise type checks.
    - Does not misidentify `null` as an object.
  - **Cons**:
    - Complexity: Slightly more complex, as it checks the prototype chain.
    - Can lead to issues with cross-frame objects where the same constructor might exist in different execution contexts.

### Benchmark Results

From the benchmark results:
- The `instanceof` approach recorded **496,715.0625 executions per second**.
- The `typeof` approach recorded **493,118.25 executions per second**.

While both methods appear to have similar performance based on these results, `instanceof` marginally outperforms `typeof` in this context.

### Other Considerations

- **Context of Use**: Depending on the use case, choosing between `typeof` and `instanceof` might not only be about performance but also about the clarity of intention in the code. If you want to check for a general object type, `typeof` is sufficient. If you need to confirm the object is an instance of a class, use `instanceof`.
- **Alternative Solutions**: 
  - **Array.isArray(value)**: If it's crucial to discern between arrays and objects, using `Array.isArray()` after either check could offer a more robust solution.
  - **Object.prototype.toString.call(value)**: This method returns a string indicating the type of the object (including special cases like `Array`, `Date`, etc.) and can provide a highly accurate type-checking mechanism, although it might come with performance trade-offs.

In conclusion, both `typeof` and `instanceof` have their merits and limitations. The choice between them depends on the application's specific needs for type identification, as well as the importance of performance in the given context.

Related benchmarks:

typeof vs instanceof (version: 1)

Comparing performance of: typeof vs instanceof

Created: 11 months ago by: Guest

Jump to the latest result

typeof

instanceof

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 11 months ago):