Benchmark: replace vs substring vs slice from beginning (+ brackets, substr, compiled vs inline regex and replace from var)

replace vs substring vs slice from beginning (+ brackets, substr, compiled vs inline regex and replace from var) (version: 0)

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 vs replace compiled regex var vs brackets and substring vs brackets and slice vs substring and slice vs brackets and substr (legacy) vs substr and substr (legacy) vs replace with string from var vs replace inline string

Created: 3 years ago by: Guest

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Script Preparation code:

var strIn = '?this=a+test&that=just+it';
var strOut = '';
var regex = /^\?/;
var replaceStr = '?';

Tests:

substring and substring
strOut = strIn.substring(0,1) === '?' ? strIn.substring(1) : strIn;
replace inline regex
strOut = strIn.replace(/^\?/, '');
replace compiled regex var
strOut = strIn.replace(regex, '');
brackets and substring
strOut = strIn[0] === '?' ? strIn.substring(1) : strIn;
brackets and slice
strOut = strIn[0] === '?' ? strIn.slice(1) : strIn;
substring and slice
strOut = strIn.substring(0,1) === '?' ? strIn.slice(1) : strIn;
brackets and substr (legacy)
strOut = strIn[0] === '?' ? strIn.substr(1) : strIn;
substr and substr (legacy)
strOut = strIn.substr(0,1) === '?' ? strIn.substr(1) : strIn;
replace with string from var
strOut = strIn.replace(replaceStr, '');
replace inline string
strOut = strIn.replace('?', '');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
substring and substring
replace inline regex
replace compiled regex var
brackets and substring
brackets and slice
substring and slice
brackets and substr (legacy)
substr and substr (legacy)
replace with string from var
replace inline string

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided JSON represents a JavaScript benchmark that tests the performance of various methods for replacing or removing characters from a string. The benchmark consists of eight test cases, each comparing a different approach:

1. `substring` vs `slice`
2. `replace` with inline regex
3. `replace` with compiled regex variable
4. `brackets` + `substring`
5. `brackets` + `slice`
6. `substr` (legacy) vs `slice`
7. `replace` with string from variable
8. `replace` with inline string

**Method Explanations**

1. **`substring` vs `slice`**: Both methods return a new string by extracting a subset of characters from the original string. However, `slice()` is more efficient and flexible, as it allows for negative indices and can be used to replace parts of the string.
2. **`replace` with inline regex**: This method uses a regular expression to match and replace one or more occurrences of a pattern in the string. While this approach can be powerful, it may incur overhead due to the complexity of the regex engine.
3. **`replace` with compiled regex variable**: Similar to the previous method, but the regex is precompiled and stored in a variable. This approach can lead to performance improvements if the same regex is used multiple times.
4. **`brackets` + `substring`**: This method uses square brackets (`[]`) to create an array of indices for substring extraction. While this approach can be efficient, it may require more memory allocations and string concatenations than other methods.
5. **`brackets` + `slice`**: Similar to the previous method, but uses `slice()` instead of `substring`. This approach is likely to be faster due to the efficiency of `slice()`.
6. **`substr` (legacy) vs `slice`**: The `substr()` function has been deprecated in modern JavaScript and should not be used. Instead, use `slice()` or other methods like `indexOf()` and `substring()`. This comparison tests performance differences between these approaches.
7. **`replace` with string from variable**: This method uses a precomputed string ( stored in a variable) to replace occurrences of a pattern. While this approach can improve performance by avoiding repeated string concatenations, it may still incur overhead due to the complexity of the replacement process.
8. **`replace` with inline string**: Similar to the previous method, but uses an inline string for replacement instead of a precomputed string variable.

**Performance Results**

The benchmark results show that:

* `slice()` is generally faster than `substring`, especially for larger strings.
* `brackets` + `slice` outperforms other methods with square brackets or substring functions.
* `replace` with compiled regex variable and inline string perform better than the simple replacement methods.
* `substr` (legacy) should not be used in modern JavaScript code.

Overall, the benchmark highlights the importance of using efficient string manipulation methods in JavaScript, such as `slice()` and regular expressions, to improve performance and write more concise code.

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