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.length vs var
(version: 0)
Comparing performance of:
accessing .length vs storing and accessing variable
Created:
5 years ago
by:
Guest
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Tests:
accessing .length
var p = new Array(1000000000) console.log(p.length);
storing and accessing variable
var p = new Array(1000000000) var l = p.length; console.log(l);
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
accessing .length
storing and accessing variable
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 benchmarking test cases. **What is being tested?** The provided JSON represents two test cases that compare the performance of accessing the length property of an array using two different approaches: 1. Directly accessing the `length` property of the array (`"accessing .length"`). 2. Storing the result of `p.length` in a variable (`"storing and accessing variable"`). **Options compared** The two options being compared are: * Option 1: Directly access the `length` property of the array using dot notation (`".length"`). * Option 2: Store the result of `p.length` in a variable, and then access it. **Pros and Cons of each approach:** 1. **Directly accessing `.length`:** * Pros: + Typically faster because it avoids the overhead of storing and retrieving a value. + Often preferred by developers due to its simplicity and readability. * Cons: + May not be as efficient for very large arrays, as it requires fetching the array length from memory. 2. **Storing and accessing variable:** * Pros: + Can provide better cache performance because the value is stored in memory once and can be reused. * Cons: + Typically slower due to the overhead of storing and retrieving a value. **Library or special JS feature usage** None of the test cases explicitly use any libraries or special JavaScript features. However, it's worth noting that the benchmark assumes that the `p` variable is an array created using the `new Array()` constructor, which is a standard JavaScript construct. **Other considerations:** * The benchmark uses a large array with 1 billion elements to ensure that any performance differences are noticeable. * The test cases measure the number of executions per second (ExecutionsPerSecond) for each option, which provides a rough estimate of the performance difference between them. * The benchmark result shows that directly accessing `.length` is slightly faster than storing and accessing a variable. **Alternatives** If you were to rewrite this benchmark with different approaches or modifications, some alternatives could include: * Using other array methods, such as `array.length`, `Array.prototype.length`, or `Array.prototype.slice()` to access the length property. * Comparing performance using other metrics, such as memory usage or CPU utilization. * Testing performance in different environments, such as Node.js, WebAssembly, or browser-specific engines like SpiderMonkey or V8.
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