String Comparison and Collation in the Intl Library

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In the software development world, handling text data is a critical component. For applications to interact effectively with users across different languages and locales, a mechanism for comparing and sorting strings is essential. However, such a task is not as straightforward as it seems.

There’s an inherent complexity involved when dealing with different languages and locales. Not every language follows the same alphabetic sequence, and certain characters have different meanings depending on the context and location. For developers, these linguistic and cultural nuances pose significant challenges.

This is where the Intl library steps in, playing a pivotal role in providing standardized string comparison and collation support. The library is an essential tool in internationalizing software, thereby bridging the gap between different languages and cultures.

String Comparison

String comparison, as the name suggests, refers to the process of comparing and sorting strings. Its significance is immense, especially when it comes to arranging data in an orderly manner, searching databases, or verifying user inputs.

However, simple character-based comparison doesn’t always cut it. With a basic ASCII comparison, the uppercase ‘A’ will always come before the lowercase ‘a’, and English sorting rules will apply to all strings, regardless of their language.

This is where the need for language-specific and culturally-aware string comparison arises. The significance of accommodating such complications is apparent when you consider the global audience that many applications have to serve.

The Intl Library

The Intl library serves as an excellent solution for language-aware string comparison. It is designed to handle internationalization and localization tasks, offering rich features to address the nuances of various languages and cultures

et string1 = "café";
let string2 = "cafe";
console.log(string1.localeCompare(string2, 'en')); // -1
console.log(string1.localeCompare(string2, 'fr')); // 0

This simple example highlights the difference between English and French string comparison rules using the Intl library.

String Comparison with the Intl Library

The Intl library offers a standardized approach to string comparison, considering language-specific rules, sorting order, case sensitivity, and accent marks. The library’s consistency in delivering sorting results based on linguistic expectations is a strong advantage.

Let’s explore more examples that illuminate different use cases.

Comparing strings in English

In English, there are rules around alphabetical order and capitalization that we are familiar with. Here, the Intl library doesn’t show much difference from a simple ASCII comparison, but it still proves useful.

let collator = new Intl.Collator('en');
let strings = ["Apple", "apple", "Banana", "banana"];
console.log(strings); // ["Apple", "apple", "Banana", "banana"]

This example shows that the library follows the general English rule where capitalized words come before their lowercase equivalents.

Ignoring accents in French

In French, accents are crucial for correct pronunciation, but sometimes you want to sort words as if they were unaccented. For that, you can use the sensitivity: 'base' option.

let collator = new Intl.Collator('fr', { sensitivity: 'base' });
let strings = ["être", "etré", "etre", "étre"];
console.log(strings); // ["etre", "etré", "étre", "être"]

In this example, words are sorted as if the accents didn’t exist.

Respecting accent differences in Spanish

In Spanish, however, you might want to maintain the distinctions caused by accents during the sorting process.

let collator = new Intl.Collator('es');
let strings = ["más", "mas", "más", "Mas"];
console.log(strings); // ["Mas", "mas", "más", "más"]

Here, the word más (meaning more) correctly comes after mas (meaning but) in the sort order.

Handling special characters in German

German includes characters like ä, ö, and ß. The Intl library correctly handles such characters when sorting.

let collator = new Intl.Collator('de');
let strings = ["Müller", "Mueller", "Muller", "müller"];
console.log(strings); // ["müller", "Muller", "Mueller", "Müller"]

In this example, Müller with an umlaut ü is correctly sorted with respect to Mueller and Muller.

These examples illustrate the versatility of the Intl library in accommodating a wide range of language-specific rules and use cases in string comparison.


Collation is an extension of string comparison. It involves the arrangement of strings based on language-specific rules and cultural conventions, factoring in aspects such as character order, case sensitivity, and accent marks.

The Intl Library and Collation

The Intl library offers robust support for collation via the Intl.Collator object. Developers can create collation instances for specific locales, ensuring accurate and culturally appropriate sorting.

let collator = new Intl.Collator('fr');
let strings = ["zèbre", "Zèbre", "zèbre"];
console.log(strings); // ["Zèbre", "zèbre", "zèbre"]

In this French example, despite ‘Z’ being capitalized, it’s sorted before the lowercase instances, reflecting French linguistic conventions.

 Working with Collation in the Intl Library

Utilizing collation in the Intl library involves creating a Collator instance with desired options, such as the locale and sensitivity. The compare() method or function is then used to compare and sort strings. Let’s dive deeper with some illustrative examples highlighting various use cases.

Case-insensitive sorting in English

In certain scenarios, you may wish to ignore the case while sorting strings. This can be achieved by using the sensitivity: 'base' option.

let collator = new Intl.Collator('en', { sensitivity: 'base' });
let strings = ["Apple", "apple", "Banana", "banana"];
console.log(strings); // ["Apple", "apple", "Banana", "banana"]

The above example sorts the strings regardless of their case, following the English alphabetical order.

Sorting French words with accent-insensitive comparison

In French, some words differ only by accents. When sorting such words, you may want to treat them as identical. The Intl library offers this functionality through the sensitivity: 'base' option.

let collator = new Intl.Collator('fr', { sensitivity: 'base' });
let strings = ["cote", "coté", "côte", "côté"];
console.log(strings); // ["cote", "coté", "côte", "côté"]

Here, words are sorted as if the accents were not present.

Case and accent-sensitive sorting in Spanish

Spanish language sorting might require maintaining the distinctions caused by both cases and accents during the process.

let collator = new Intl.Collator('es', { sensitivity: 'case' });
let strings = ["más", "mas", "Más", "Mas"];
console.log(strings); // ["Mas", "mas", "Más", "más"]

In this example, both the capitalization and accent marks are considered in the sorting order.

Using numeric collation in German

Numeric collation comes in handy when sorting strings that contain numbers. It ensures that numbers are sorted based on their numeric value, rather than the individual digits.

let collator = new Intl.Collator('de', { numeric: true });
let strings = ["Item 2", "Item 11", "Item 1", "Item 10"];
console.log(strings); // ["Item 1", "Item 2", "Item 10", "Item 11"]

Here, the strings are sorted considering the numeric value of the numbers, which can be particularly useful in inventory management or file sorting applications.

These examples illustrate how the Intl library’s Collator object can be used to handle various collation tasks, highlighting its flexibility in adapting to different language rules and requirements.

Further Reading


String comparison and collation are integral to internationalized software. They enhance user experiences, allow accurate data organization, and importantly, respect cultural nuances. The Intl library’s capabilities address these challenges, delivering consistent and accurate results across various languages and locales.

As developers, it’s our responsibility to ensure our applications serve the diverse cultural expectations of our user base. By utilizing the Intl library’s features, we can create more inclusive, accessible, and user-friendly software. Happy coding!

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