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Spread vs Assign Object Copy
(version: 0)
Comparing performance of:
Spread vs Assign
Created:
5 years ago
by:
Guest
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Tests:
Spread
const a = {mix1: "a", mix2: "b", mix3: { mox1: "a", mox2: "b" }}; const b = { ...a };
Assign
const a = {mix1: "a", mix2: "b", mix3: { mox1: "a", mox2: "b" }}; const b = Object.assign({}, a);
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
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Test case name
Result
Spread
Assign
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the provided benchmark and explain what's being tested, compared, and their pros and cons. **Benchmark Definition** The benchmark is testing two approaches to create a copy of an object in JavaScript: using the spread operator (`{ ...a }`) and using `Object.assign()`. **Options Compared** 1. **Spread Operator ( `{ ...a }` )**: This method creates a new object by iterating over the properties of the original object `a` and copying each property to the new object. 2. **Object.assign() ( `const b = Object.assign({}, a);` )**: This method creates a new object by copying all enumerable own properties from the source object `a` to the target object `b`. **Pros and Cons** * **Spread Operator**: + Pros: concise, readable, works with objects that have nested properties. + Cons: only works with objects (not arrays), can be slower than `Object.assign()` for very large objects. * **Object.assign()**: + Pros: widely supported, fast, works with both objects and arrays. + Cons: less readable, requires explicit creation of an empty object. **Library and Special JS Features** In this benchmark, the `Spread` test case uses the spread operator (`{ ...a }`), which is a modern JavaScript feature introduced in ECMAScript 2018 (ES8). The `Assign` test case uses the `Object.assign()` method, which has been available since ECMAScript 2009 (ES5). **Other Considerations** * **Performance**: Both methods have similar performance characteristics for small to medium-sized objects. However, for very large objects, the spread operator might be slower due to its iterative nature. * **Memory Usage**: The spread operator creates a new object in memory, whereas `Object.assign()` copies properties from the source object without creating a new object. This can affect memory usage for large objects. **Alternatives** If you want to explore other approaches, here are some alternatives: 1. **Array.prototype.slice()**: You can use `Array.prototype.slice()` to create an array copy of an object's values. 2. **Object.create()**: You can use `Object.create()` to create a new object with a specific prototype. 3. **JSON.parse(JSON.stringify())**: This method creates a deep copy of an object by serializing it as JSON and then deserializing the string back into an object. Keep in mind that these alternatives may have different performance characteristics, memory usage, or readability compared to the spread operator and `Object.assign()` methods.
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