Benchmark: slice vs substr vs substring vs replace

Script Preparation code:

var example = 'there is no spoon'

Tests:

slice
var result = example.slice(5, example.lenght)
substr
var result = example.substr(5, example.lenght)
substring
var result = example.substring(5, example.lenght)
replace
var result = example.replace('there', '')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
substr
substring
replace

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Measuring the performance of different JavaScript methods for string manipulation is crucial in understanding how various browsers and environments optimize these operations.

The provided benchmark compares `slice`, `substr`, and `substring` methods when used with only a start index, as well as the `replace` method. Here's an explanation of each method:

1.  **`slice()`**: Returns a new string that includes all characters from the current position to the end of the string.

*   Pros: More flexible than `substr` or `substring`, allows specifying both start and end indices.
    *   Cons: Creates a new string object, which can be memory-intensive for large strings.
2.  **`substr()`**: Returns a new string that includes all characters from the current position to the specified length.

*   Pros: More efficient than `slice()` because it returns only the requested number of characters, rather than an entire new string.
    *   Cons: Fixed-length slicing can lead to truncation if the requested length exceeds the remaining characters in the string.
3.  **`substring()`**: Returns a new string that includes all characters from the current position to the specified end index.

*   Pros: Similar to `substr`, but allows specifying an end index, which can be useful for cases where you need to slice from both the start and end of the string.
    *   Cons: Can lead to performance issues if used with large strings due to the creation of a new string object.
4.  **`replace()`**: Replaces occurrences of a specified pattern in the original string with another value.

*   Pros: Not a slicing method, but rather a replacement operation that can be more efficient than creating and manipulating individual characters or substrings.
    *   Cons: Requires careful consideration to avoid unexpected replacements or modifications to the original string.

The provided benchmark results show that:

*   `substr` outperforms both `slice()` and `substring()` methods, likely due to its fixed-length slicing approach.
*   The performance of these methods can be influenced by factors such as browser version, platform, and available memory.

Other alternatives for string manipulation in JavaScript include:

*   **Regular expressions**: Useful for complex pattern matching, text extraction, or validation, but often slower than simple string operations due to the overhead of compiling and executing regex patterns.
*   **Array methods**: Such as `slice()`, `concat()`, and `substring()` (when used on arrays), which can be more efficient than individual string manipulation for certain use cases.

To improve performance in JavaScript:

*   Use caching mechanisms, such as memoization or caching libraries, to store frequently accessed values.
*   Leverage browser-specific optimizations, like `String.prototype.slice()` and `String.prototype.replace()`, which can provide better performance on specific platforms.
*   Optimize for memory usage by using techniques like avoiding unnecessary string allocations or using more efficient data structures.
*   Profile your application's performance using tools like Chrome DevTools or Node.js Inspector to identify bottlenecks and areas for improvement.

Related benchmarks:

slice vs substr vs substring vs replace (version: 0)

Compares slice, substr and substring to each other when there is only a start index

Comparing performance of: slice vs substr vs substring vs replace

Created: 5 years ago by: Registered User

Jump to the latest result

slice

substr

substring

replace

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):