Benchmark: Intl.NumberFormat cache vs new Intl.NumberFormat vs toLocaleString currency

Script Preparation code:

window.formatCache = new Map();
window.formatNumber = function(value, options) {
  var key = JSON.stringify(options);
  var formatter = window.formatCache.get(key);
  if (!formatter) {
    formatter = new Intl.NumberFormat(options.locale, options);
    window.formatCache.set(key, formatter);
  }
  return formatter.format(value);
};

Tests:

cached Intl.NumberFormat instance
window.formatNumber(3_950_219.56, { locale:'pt-BR', style: 'currency', currency: 'BRL' });
new Intl.NumberFormat
new Intl.NumberFormat('pt-BR', { style: 'currency', currency: 'BRL' }).format(3_950_219.56);
Number.prototype.toLocaleString
(3_950_219.56).toLocaleString('pt-BR', { style: 'currency', currency: 'BRL' });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
cached Intl.NumberFormat instance
new Intl.NumberFormat
Number.prototype.toLocaleString

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:132.0) Gecko/20100101 Firefox/132.0

Browser/OS: Firefox 132 on Windows

View result in a separate tab

Test name	Executions per second
cached Intl.NumberFormat instance	1633937.5 Ops/sec
new Intl.NumberFormat	65559.7 Ops/sec
Number.prototype.toLocaleString	59420.6 Ops/sec

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

LLMs can make mistakes. Check important info.

The benchmark compares three different methods of formatting numbers as currency in JavaScript, specifically using the Brazilian real (BRL) currency and the Portuguese (Brazil) locale (`pt-BR`). The goal is to determine the performance differences between these methods in terms of execution speed.

### Methods Being Compared:

1. **Cached `Intl.NumberFormat` Instance**:
   - **Benchmark Definition**: `window.formatNumber(3_950_219.56, { locale:'pt-BR', style: 'currency', currency: 'BRL' });`
   - **Test Name**: cached Intl.NumberFormat instance
   - **Description**: This method utilizes a cache to store `Intl.NumberFormat` instances based on their options. When the same formatting options are requested again, the cached instance is reused instead of creating a new one.
   - **Pros**:
     - Efficient for repeated formatting with the same options, preventing the overhead of creating multiple formatters.
     - Significantly faster for scenarios where the same formatting options are used multiple times.
   - **Cons**:
     - Requires additional memory to store cached instances.
     - Initial caching overhead on the first request.

2. **New `Intl.NumberFormat` Instance**:
   - **Benchmark Definition**: `new Intl.NumberFormat('pt-BR', { style: 'currency', currency: 'BRL' }).format(3_950_219.56);`
   - **Test Name**: new Intl.NumberFormat
   - **Description**: This method creates a new `Intl.NumberFormat` object every time it's called for the specified options.
   - **Pros**:
     - Simplicity; you don’t need to manage a cache.
     - Suitable for one-off formatting needs where the options may vary frequently.
   - **Cons**:
     - Inefficient for repeated formatting with the same options due to the overhead of creating a new formatter each time.
     - Slower performance in scenarios with repetitive calls.

3. **`Number.prototype.toLocaleString`**:
   - **Benchmark Definition**: `(3_950_219.56).toLocaleString('pt-BR', { style: 'currency', currency: 'BRL' });`
   - **Test Name**: Number.prototype.toLocaleString
   - **Description**: This method is a built-in JavaScript function that formats a number according to locale-specific rules, including currency format in this case.
   - **Pros**:
     - Very straightforward and easy to use for single-number formatting.
     - Part of the native `Number` prototype, ensuring compatibility across different environments.
   - **Cons**:
     - It may be less performant compared to using cached formatters due to possible internal instantiation of formatters (implementation-specific).
     - The flexibility can lead to less optimized results than a specifically cached format.

### Benchmark Results Summary:
From the most recent benchmark results, we can see significant performance disparities:
- **Cached `Intl.NumberFormat` instance**: 857,920.63 executions per second, which is the fastest.
- **`Number.prototype.toLocaleString`**: 30,095.96 executions per second, which is much slower than the cached version but faster than the regular instantiation of formatter.
- **New `Intl.NumberFormat`**: 28,354.07 executions per second, the slowest of all three methods.

### Alternatives:
- **Manual Formatting**: You could manually build a number string using string manipulation. However, this would require implementing localization rules and could easily become error-prone or fail to adapt to different locales.
- **External Libraries**: Libraries such as `numeral.js`, `accounting.js`, or ` Intl.js` offer additional formatting capabilities with their own performance characteristics. These might be more complex and could introduce additional dependencies, but they can also provide more flexibility compared to built-in options.
- **Performance Optimizations**: Other patterns might include either memoization mechanisms or custom implementation of caching strategies beyond just relying on `Intl.NumberFormat`.

Overall, developers should choose a method based on their specific use case, considering factors like frequency of calls, performance requirements, and memory constraints in their applications.

Related benchmarks:

Intl.NumberFormat cache vs new Intl.NumberFormat vs toLocaleString currency (version: 1)

Comparing performance of: cached Intl.NumberFormat instance vs new Intl.NumberFormat vs Number.prototype.toLocaleString

Created: one month ago by: Guest

Jump to the latest result

cached Intl.NumberFormat instance

new Intl.NumberFormat

Number.prototype.toLocaleString

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):