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Object.assign vs Spread syntax vs for...in statement for clone
(version: 0)
Comparing performance of:
Object.assign vs Spread syntax vs for...in statement
Created:
4 years ago
by:
Registered User
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Tests:
Object.assign
const obj1 = { a:'hello', b: 'world', c:'!' }; const obj2 = Object.assign(obj1)
Spread syntax
const obj1 = { a:'hello', b: 'world', c:'!' }; const obj2 = { ...obj1 }
for...in statement
const obj1 = { a:'hello', b: 'world', c:'!' }; const obj2 = {} for (const key in obj1) { obj2[key] = obj1[key] }
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Suite status:
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Run tests (3)
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Test case name
Result
Object.assign
Spread syntax
for...in statement
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Slowest:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the benchmark and its test cases. **Benchmark Definition JSON** The benchmark is designed to compare three approaches for cloning an object: `Object.assign`, `Spread syntax` (also known as the "rest operator" or ellipsis syntax), and `for...in statement`. **Test Cases** There are three individual test cases, each representing one of the cloning methods: 1. **`Object.assign`**: This method uses the `Object.assign()` function to create a new object by copying properties from an existing object (`obj1`) into a new object (`obj2`). The `Object.assign()` function iterates over the enumerable properties of `obj1` and copies each property to `obj2`. 2. **`Spread syntax`**: This method uses the spread operator (`{ ... }`) to create a new object by copying all own enumerable properties from an existing object (`obj1`) into a new object (`obj2`). The spread operator creates a new array-like object that contains all the property names of `obj1`, and then iterates over this array to copy each property to `obj2`. 3. **`for...in statement`**: This method uses a `for...in` loop to iterate over the enumerable properties of an object (`obj1`) and copies each property to a new object (`obj2`). The `for...in` loop iterates over all properties, including inherited ones. **Pros and Cons** Here's a brief overview of the pros and cons of each approach: * **`Object.assign`**: + Pros: widely supported, efficient, and flexible. + Cons: can be slower than other methods due to its iterative nature. * **`Spread syntax`**: + Pros: concise, expressive, and modern. + Cons: may not work correctly with non-enumerable properties or inherited ones. * **`for...in statement`**: + Pros: allows for fine-grained control over property iteration. + Cons: can be slower than other methods due to its iterative nature and potential overhead of checking property existence. **Library Usage** None of the test cases use any libraries, as they only utilize built-in JavaScript features. **Special JS Features or Syntax** * None of the test cases use any special JavaScript features or syntax beyond what's described above. However, it's worth noting that modern JavaScript engines are very good at optimizing and executing these basic cloning methods. **Other Alternatives** There are other ways to clone an object in JavaScript, such as using `JSON.parse(JSON.stringify(obj1))`, but these approaches may have their own trade-offs (e.g., slower performance or potential issues with nested objects). For example, you could also use: * `Object.create(null)` or `Object.create({}, ...)`: These methods create a new object without any prototype chain, which can be beneficial in certain cases. * `Array.prototype.slice.call()` or `Function.prototype.apply()`: These methods can be used to create an array-like object from another iterable, but may not be the best choice for cloning objects. However, these alternatives are generally less intuitive and more low-level than the three test cases described above.
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