Benchmark: Is it worth checking for empty string before replace with regex?

Script Preparation code:

const arr = []
for(let i = 1; i < 1000; i++) {
    arr.push(' '.repeat(i))
}
for(let i = 1; i < 100; i++) {
    arr.push('');
    arr.push(' text '.repeat(i))
}

const run = (fn) => {
    const result = []
    for(const val of arr) {
        result.push(fn(val));
    }
    return result
}

Tests:

trim and always replace
run((val) => val.trim().replace(/\s+/g, ' '))
trim and conditionally replace
run((val) => { const trimmed = val.trim(); return trimmed && trimmed.replace(/\s+/g, ' '); })
trim and conditionally replace with if
run((val) => { const trimmed = val.trim(); if (trimmed === '') { return ''; } else { return trimmed.replace(/\s+/g, ' '); } })
always replace and trim
run((val) => val.replace(/\s+/g, ' ').trim())
conditionally trim and conditionally replace
run((val) => { if(val === '') { return val; } const trimmed = val.trim(); if (trimmed === '') { return trimmed; } else { return trimmed.replace(/\s+/g, ' '); } })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
trim and always replace
trim and conditionally replace
trim and conditionally replace with if
always replace and trim
conditionally trim and conditionally replace

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one month ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:136.0) Gecko/20100101 Firefox/136.0

Browser/OS: Firefox 136 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
trim and always replace	2453.7 Ops/sec
trim and conditionally replace	2604.8 Ops/sec
trim and conditionally replace with if	2607.7 Ops/sec
always replace and trim	2255.7 Ops/sec
conditionally trim and conditionally replace	2641.4 Ops/sec

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

LLMs can make mistakes. Check important info.

The benchmark titled **"Is it worth checking for empty string before replace with regex?"** tests different approaches to handling strings in JavaScript, particularly with respect to trimming whitespace and replacing sequences of whitespace characters with a single space using regular expressions.

### Options Compared

1. **Trim and always replace**:
   ```javascript
   run((val) => val.trim().replace(/\s+/g, ' '))
   ```
   - This approach first trims the input string and then applies regex replacement on the trimmed result. 
   - **Pros**: Simple and concise; handles any string, ensuring leading and trailing whitespace is removed.
   - **Cons**: Performs regex replacement even on empty strings or strings that become empty after trimming, which may be unnecessary.

2. **Trim and conditionally replace**:
   ```javascript
   run((val) => {
       const trimmed = val.trim(); 
       return trimmed && trimmed.replace(/\s+/g, ' ');
   })
   ```
   - Similar to the first, but this only applies the regex replacement if the trimmed string is not empty.
   - **Pros**: More efficient for empty strings; avoids unnecessary processing.
   - **Cons**: Still checks the condition after trimming; might introduce a slight overhead in branching.

3. **Trim and conditionally replace with if**:
   ```javascript
   run((val) => {
       const trimmed = val.trim();
       if (trimmed === '') {
           return ''; 
       } else {
           return trimmed.replace(/\s+/g, ' ');
       }
   })
   ```
   - This version explicitly checks if the trimmed string is empty, using an `if` statement.
   - **Pros**: Clear logic; straightforward handling of empty cases.
   - **Cons**: Slightly more verbose and may introduce a little more overhead compared to the previous approach.

4. **Always replace and trim**:
   ```javascript
   run((val) => val.replace(/\s+/g, ' ').trim())
   ```
   - Here, the regex replacement is applied first, followed by trimming.
   - **Pros**: This can be simpler when working with strings that are only whitespace, as it handles replacement directly.
   - **Cons**: Similar issue with unnecessary processing for empty results; could cause inefficiency.

5. **Conditionally trim and conditionally replace**:
   ```javascript
   run((val) => {
       if(val === '') {
           return val;
       }
       const trimmed = val.trim();
       if (trimmed === '') {
           return trimmed;
       } else {
           return trimmed.replace(/\s+/g, ' ');
       }
   })
   ```
   - This approach checks both for an empty string and for an empty value after trimming.
   - **Pros**: Most thorough in handling edge cases effectively.
   - **Cons**: Increased complexity and verbosity may not be necessary for some use cases.

### Regular Expressions and their Purpose

The regex used in these benchmarks (`/\s+/g`) matches one or more whitespace characters globally. The purpose is to normalize any sequences of whitespace (spaces, tabs, line breaks) to a single space. This can help maintain clean formatting when dealing with user input or data processing.

### Considerations

- **Performance**: There is a trade-off between clarity and performance. Simpler methods might be faster due to reduced branching, while more complex methods handle edge cases explicitly.
- **Use Cases**: Depending on the expected input (e.g., user-generated content), some methods may be more appropriate than others.
- **Readability**: Maintaining readable and maintainable code is crucial, so overly complex solutions may not be worth marginal performance benefits.

### Alternatives

1. **Using Libraries**:
   - There are libraries like **Lodash** that provide utility functions (e.g., `_.trim`, `_.replace`) which can be used for such operations, providing additional robustness.

2. **Native String Methods**:
   - In ES6 onward, developers can use `String.prototype.split` to achieve similar results without regex, though this might not be as concise or efficient.

3. **Using Functional Programming Concepts**:
   - Higher-order functions like `map` can also be leveraged alongside the mentioned methods for batch processing lists of strings if applicable.

In summary, the benchmark primarily illustrates different methods of handling whitespace in strings, with a focus on efficiency and edge case handling, while also providing insights into performance considerations in JavaScript string manipulation.

Related benchmarks:

Is it worth checking for empty string before replace with regex? (version: 1)

Comparing performance of: trim and always replace vs trim and conditionally replace vs trim and conditionally replace with if vs always replace and trim vs conditionally trim and conditionally replace

Created: one month ago by: Registered User

Jump to the latest result

trim and always replace

trim and conditionally replace

trim and conditionally replace with if

always replace and trim

conditionally trim and conditionally replace

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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