This benchmark from MeasureThat.net compares three string manipulation methods in JavaScript: slice, substr, and substring, as well as a “no operation” (Nop) case where the string is simply assigned without manipulation. Each method is tested in terms of performance, specifically how many times they can be executed per second on the given system (Safari 18 on macOS).

Comparison of Approaches:

1. slice:

   • Signature: string.slice(startIndex)
   • Description: Extracts a section of a string between the specified startIndex and the end of the string.
   • Pros:
     • Can accept negative indices to count from the end of the string.
   • Cons:
     • Might be less intuitive for beginners who expect it to behave similarly to other string methods.

2. substr:

   • Signature: string.substr(startIndex)
   • Description: Extracts characters from a string starting at startIndex and continuing until the end of the string.
   • Pros:
     • Simpler for extracting substrings when the length to be extracted is not specified, as it always runs until the end.
   • Cons:
     • Considered deprecated in the latest ECMAScript standards, which may lead to compatibility issues in future JavaScript engines.

3. substring:

   • Signature: string.substring(startIndex)
   • Description: Similar to slice, but does not accept negative indices.
   • Pros:
     • More intuitive for users familiar with the concept of sections of a string based strictly on character position.
   • Cons:
     • Cannot handle negative indices, which can be limiting in some contexts.

4. Nop:

   • Description: Represents a baseline case with no operation performed. It helps understand the performance difference by providing a control case against which the other methods can be evaluated.
   • Utility: By executing a simple assignment to result, it establishes a benchmark for the simplest case without string manipulation.

Performance Results:

From the benchmark results, we can see how each method performed in terms of executions per second:

• Nop: 517,870,176 executions/second
• substring: 508,300,992 executions/second
• slice: 503,419,872 executions/second
• substr: 62,158,564 executions/second

Observations:

• The Nop has the highest execution rate since it performs no computation.
• substring and slice are very close in terms of performance, while substr significantly lags behind.
• The performance difference between substring and slice is not substantial, indicating both are optimized well in the underlying JavaScript engine in Safari.
• substr, being deprecated, suggests engineers may want to avoid it in favor of the other two methods.

Other Considerations:

• Deprecation of substr: Since this function is deprecated, it is advisable for developers to refrain from using it in new code. Instead, using slice or substring can enhance code maintainability and compatibility with future JavaScript standards.
• Negative Index Support: The ability of slice to handle negative indices may be a decisive factor for developers who require flexibility in string manipulation.

Alternatives:

In addition to these string manipulation methods, there are other approaches for handling strings in JavaScript:

• Regular Expressions: Using RegExp for complex string searches and manipulations.
• String.prototype.replace(): For substitution operations.
• String.prototype.split(): For dividing strings based on a delimiter.
• Template Literals: Using backticks to create multi-line strings or include expressions within strings.

When deciding which method to use, software engineers should consider readability, performance, and future compatibility in their codebases.