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index === 0 vs lastindexof( ,0) === 0
(version: 0)
Comparing performance of:
lastIndexOf vs indexOf
Created:
4 years ago
by:
Guest
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Tests:
lastIndexOf
var str = "Hello world, welcome to the universe."; var n = str.lastIndexOf("Hello", 0) === 0;
indexOf
var str = "Hello world, welcome to the universe."; var n = str.indexOf("Hello") === 0;
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
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Test case name
Result
lastIndexOf
indexOf
Fastest:
N/A
Slowest:
N/A
Latest run results:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
I'll break down the provided benchmark definition and test cases, explaining what's being tested, the pros and cons of each approach, and other considerations. **Benchmark Definition** The benchmark measures the performance difference between two string methods: `lastIndexOf` and `indexOf`. The specific usage is to check if a substring ("Hello") appears at the start (`0`) of a given string ("Hello world, welcome to the universe."). **Options Compared** Two options are being compared: 1. **`str.lastIndexOf("Hello", 0) === 0`**: This method uses `lastIndexOf` with an optional second argument to specify the starting index for the search. 2. **`str.indexOf("Hello") === 0`**: This method uses `indexOf`, which returns `-1` if the substring is not found, and returns its position if it's found. **Pros and Cons of Each Approach** Both methods are designed to find a specific character in a string. However, there are some differences: * **`lastIndexOf` with an optional second argument**: This method can be faster for certain cases because it doesn't require creating a new array or performing additional checks. * `indexOf`: This method always returns the position of the first occurrence of the specified value, and if not found, it returns `-1`. However, since we're interested in whether the substring appears at the start, using `indexOf` with `=== 0` can provide a direct answer without having to perform additional checks. However, since both methods are checking for the position of the first occurrence (`=== 0`), this might not be an ideal comparison. A better approach would be to compare these two methods in scenarios where one is guaranteed to be faster than the other (e.g., when searching for a substring within a large string). **Library and Special JS Features** In neither case do we see any libraries or special JavaScript features being used. **Other Alternatives** If you wanted to test similar benchmarks, here are some alternatives: * **`str.includes("Hello")`**: This method returns `true` if the substring is found anywhere in the string. * **`str.indexOf("Hello", 1)`**: This method searches for the substring starting from an index greater than 0. **Benchmark Preparation Code and Test Cases** The provided script preparation code is empty, which means that no setup or initializations are necessary before running the test. The test cases provide two examples: * **`lastIndexOf`**: Tests `str.lastIndexOf("Hello", 0) === 0`. * **`indexOf`**: Tests `str.indexOf("Hello") === 0`. **Benchmark Result** The latest benchmark result shows that Chrome 100 on a desktop platform (Mac OS X 10.15.7) executed the test with `lastIndexOf` approximately 2.3 times faster than the test with `indexOf`.
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