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index vs lastindexof (last index)
(version: 0)
Comparing performance of:
lastIndexOf vs indexOf
Created:
3 years ago
by:
Guest
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Script Preparation code:
var str = "a".repeat(1e6) + "b";
Tests:
lastIndexOf
var n = str.lastIndexOf("b");
indexOf
var n = str.indexOf("b");
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
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the benchmark and explain what's being tested. **Benchmark Overview** The benchmark compares two string methods: `indexOf` and `lastIndexOf`. The test case uses a single variable, `n`, to store the result of searching for the substring `"b"` within the prepared string `"a".repeat(1e6) + "b"`. This string is generated using the `repeat` method, which repeats the preceding expression (in this case, `"a"`) one million times. **Options Compared** The benchmark compares two options: 1. **`indexOf`**: This method searches for the first occurrence of the specified value within the string and returns its position. 2. **`lastIndexOf`**: This method searches for the last occurrence of the specified value within the string and returns its position. **Pros and Cons of Each Approach** Both methods have their advantages: * **`indexOf`**: + Pros: Faster, as it only needs to scan one side of the string. + Cons: Returns the position of the first occurrence if multiple occurrences exist; no guarantee that the result is the last index. * **`lastIndexOf`**: + Pros: Guarantees to return the last index, but may be slower due to scanning the entire string. + Cons: May be slower than `indexOf` for strings with fewer matches. **Library and Special JS Features** Neither of these methods rely on external libraries. However, it's worth noting that the test case uses the arrow function syntax (`=>`) which is supported by modern JavaScript engines (including those used in Chrome 108). This feature was introduced in ECMAScript 2015 (ES6). **Other Considerations** When choosing between `indexOf` and `lastIndexOf`, consider the use case: * If you need to find the first occurrence of a value, `indexOf` is likely sufficient. * If you need to find the last occurrence of a value or guarantee the result, `lastIndexOf` might be more suitable. **Alternatives** Other string methods that could be compared in a benchmark include: * `search()`: Similar to `indexOf`, but returns -1 if not found. * `match()`: Returns an array containing all matches; can be useful for regular expressions. * `split()` and `concat()`: These methods can be used to create substrings or concatenate strings, which might be relevant in certain optimization scenarios. Keep in mind that the choice of method depends on the specific use case and performance requirements.
Related benchmarks:
index vs lastindexof startsWith
index vs lastindexof empty
index vs lastindexof empty with startIndex set to 0
index vs lastindexof (for right biased values)
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