Benchmark: replace vs substring at the end

replace vs substring at the end (version: 1)

Test the performance of replace() vs substring() vs slice() when replacing a char at the beginning of a (in this case uri query-)string that may or may not be there. Added the combined brackets[ ] + substr() method, since it's always the first char we wan't to pop off. Inspired by https://jsperf.com/replace-or-substr. Note: could not get 'let' and 'const' to work. Well, too bad...

Comparing performance of: substring and substring vs replace inline regex

Created: one year ago by: Guest

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Script Preparation code:

var strIn = '123456ms';
var strOut = '';

Tests:

substring and substring
strOut = strIn.substr(0, strIn.length-2);
replace inline regex
strOut = strIn.replace("ms", "");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
substring and substring
replace inline regex

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:148.0) Gecko/20100101 Firefox/148.0

Browser/OS: Firefox 148 on Windows

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Test name	Executions per second
substring and substring	301487200.0 Ops/sec
replace inline regex	41421548.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

The benchmark test “replace vs substring at the end” evaluates the performance of different string manipulation methods in JavaScript, specifically when removing characters from the end of a string. The two primary methods being compared are `substring()` and `replace()`, with a note on `substr()` being added for consideration.

### Options Compared:
1. **`substring()` Method**
   - **Usage**: The test case uses `strOut = strIn.substr(0, strIn.length-2);`.
   - **Description**: This method extracts a portion of a string between two specified indices. In this context, it is used to create a substring of `strIn` that effectively removes the last two characters (`ms`), assuming the length of `strIn` is greater than 2.
   - **Performance Result**: It achieved a higher execution rate of 11,789,116 executions per second.

2. **`replace()` Method**
   - **Usage**: The benchmark uses `strOut = strIn.replace("ms", "");`.
   - **Description**: This method searches for a specified value and replaces it with a provided replacement. In this case, it searches for the string `"ms"` and replaces it with an empty string, effectively removing it if present.
   - **Performance Result**: This approach achieved 10,297,044 executions per second, which is lower than the `substring()` method for this use case.

### Pros and Cons of Each Approach:
- **`substring()` Pros**:
  - Directly works with indices, which can make it easier to manipulate specific parts of the string without having to search.
  - Potentially faster for operations where you know the exact characters to remove.

- **`substring()` Cons**:
  - Less flexible if you are looking to replace varying substrings that may not be at the end of the string.

- **`replace()` Pros**:
  - More flexible as it can target specific patterns or values within the string, making it useful for more complex replacements.
  - Supports regular expressions, allowing for pattern-based string modifications.

- **`replace()` Cons**:
  - Searching for a substring can incur additional overhead compared to directly slicing off characters, especially if the substring is fixed in position (like at the end of the string).
  - May be slower in scenarios where you're replacing known values at a predictable string position.

### Other Considerations:
- The test also briefly mentions that `let` and `const` were not utilized, which suggests that the benchmark might be using older syntax (like `var`), although it's not directly relevant for performance comparison.

### Alternatives:
- **`slice()` Method**: Similar to `substring()`, `slice()` can also be used to extract parts of the string. It has a more consistent use case with negative indices, allowing you to easily remove characters from the end (e.g., `strIn.slice(0, -2)`).
  
- **Regular Expressions**: More intricate string manipulations involving patterns can be accomplished through regular expressions, expanding the capabilities beyond simple replacements.

In conclusion, while `substring()` proved to be more efficient for this specific test of removing fixed characters from a string's end, the choice of method should align with the specific requirements of the task at hand, taking into account factors like flexibility, readability, and performance.

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