Benchmark: .replace vs .lastIndexOf + .substring

Tests:

replace
const str = ".path|otherPart" const result = str.replace(new RegExp(`(\.|^)path$`), "");
indexof
const str = ".path|otherPart" const index = str.lastIndexOf("path"); const result = str.substring(index + "path".length, str.length);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
replace
indexof

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark and the different approaches being compared.

**Benchmark Overview**

The benchmark tests two JavaScript methods: `String.prototype.replace()` and `String.prototype.lastIndexOf() + String.prototype.substring()`. The goal is to determine which approach is faster for a specific use case: replacing a substring with another string that matches at least one character from the original substring (the "path" part).

**Options being Compared**

There are two options being compared:

1. **`String.prototype.replace()`**: This method replaces occurrences of a pattern in a string. In this case, the pattern is `\`.path|otherPart\`, which means any occurrence of either ".path" or "otherPart". The `new RegExp()` constructor creates a regular expression object that matches exactly one of these patterns.
2. **`String.prototype.lastIndexOf() + String.prototype.substring()`**: This approach involves two separate operations:
	* `lastIndexOf("path")`: Finds the index of the last occurrence of the substring "path" in the string. If not found, returns -1.
	* `substring(index + "path".length, str.length)`: Returns a new string that includes all characters from the index after the last "path" character to the end of the original string.

**Pros and Cons**

Here are some pros and cons for each approach:

**`String.prototype.replace()`**

Pros:

* Faster, since it only needs to iterate over the string once.
* More efficient, as it avoids creating intermediate strings or indices.

Cons:

* May not be as readable, especially if the regular expression pattern is complex.
* Can be slower for large strings with many replacements.

**`String.prototype.lastIndexOf() + String.prototype.substring()`**

Pros:

* More readable, since each step is performed separately and clearly.
* Can be faster for small or medium-sized strings with few occurrences of "path".

Cons:

* Slower, since it needs to perform two separate operations.
* Creates intermediate indices or strings, which can consume more memory.

**Library and Special JS Features**

There are no libraries explicitly mentioned in the benchmark. However, `String.prototype.replace()` uses regular expressions (regex), which is a standard JavaScript feature.

**Special JS Feature: String.prototype.replace() with regex**

`String.prototype.replace()` allows using regular expressions to match patterns in strings. The `\.` and `\|` characters are escape sequences that treat them as literal characters instead of special characters. The `.*` pattern matches any character (including newlines) 0 or more times.

**Other Alternatives**

If the benchmark is trying to determine which approach is faster for similar use cases, other alternatives might include:

* Using a different regex pattern or syntax
* Employing other string replacement methods, such as `String.prototype.replaceAll()` (not supported in older browsers)
* Implementing custom string replacement logic using loops and string manipulation functions

Keep in mind that the choice of approach ultimately depends on the specific requirements and constraints of your project.

Related benchmarks:

.replace vs .lastIndexOf + .substring (version: 0)

Comparing performance of: replace vs indexof

Created: 3 years ago by: Guest

Jump to the latest result

replace

indexof

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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