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InstanceOf vs String type vs Symbol
(version: 0)
Measure the performance of instanceOf operator vs comparing a basic string type and vs Symbol comparison.
Comparing performance of:
instanceof vs string type vs string type + undefined vs property vs symbol
Created:
4 years ago
by:
Guest
Jump to the latest result
HTML Preparation code:
<script> var S = Symbol('symbol') class TestClass { constructor() { this.a = 2; this.t = 'mesh'; this.s = S } } </script>
Script Preparation code:
var obj = new TestClass();
Tests:
instanceof
obj instanceof TestClass;
string type
obj.t === 'mesh'
string type + undefined
obj.t !== undefined
property
obj.a !== undefined
symbol
obj.s === S
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (5)
Previous results
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Test case name
Result
instanceof
string type
string type + undefined
property
symbol
Fastest:
N/A
Slowest:
N/A
Latest run results:
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Autogenerated LLM Summary
(model
gemma2:9b
, generated one year ago):
This benchmark compares different ways to check if an object is of the correct type or has specific properties in JavaScript. Here's a breakdown: **Options Compared:** * **`instanceof TestClass`**: This checks if an object is an instance of a particular class (`TestClass` in this case). It's a traditional way to verify object type but can be less performant than other methods. * **`obj.t === 'mesh'`**: This directly compares the value of the property `t` with the string 'mesh'. This is simple and efficient if you know the exact property value you're looking for. * **`obj.t !== undefined`**: This checks if the property `t` exists and has a defined value (not `undefined`). While it works, it doesn't guarantee the property has the expected value. * **`obj.a !== undefined`**: Similar to above, but checks for the existence of property `a`. * **`obj.s === S`**: This compares the value of the symbol property `s` with the pre-defined symbol `S`. **Pros and Cons:** | Method | Pros | Cons | |---|---|---| | `instanceof` | Clear type check, widely understood | Can be slower than direct property comparison | | String Comparison (`===`) | Fast and efficient if you know the exact value | Only works for known values; not suitable for complex object checks | | Property Existence Check (`!== undefined`) | Simple to implement | Doesn't guarantee the correct value, only existence | **Other Considerations:** * **Symbols**: Symbols are unique identifiers in JavaScript, often used to create private properties. Comparing with symbols can be efficient but might not be as intuitive as other methods. * **Benchmarking Context**: The performance difference between these methods can vary depending on factors like the size of the object, the number of comparisons, and the specific JavaScript engine being used. **Alternatives:** * **Type Guards**: TypeScript offers type guards, which allow you to narrow down the type of an object based on certain conditions, improving code clarity and performance. * **Reflection (Use with Caution)**: JavaScript provides reflection mechanisms (e.g., `Object.prototype.hasOwnProperty`) that can be used for introspection. However, they can be less performant and are generally avoided for critical performance paths. Let me know if you have any more questions!
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