# Intl.Collator

The `Intl.Collator` object enables language-sensitive string comparison. It is useful for sorting strings in a way that respects the rules of a specific language (e.g., handling accents, specific alphabet orders).

## 1. Basic Usage

The `compare` method of a `Collator` instance returns a number indicating how `string1` compares to `string2` according to the sort order of the Collator object.

*   Negative number: `string1` comes before `string2`.
*   Positive number: `string1` comes after `string2`.
*   Zero: They are considered equal.

```javascript
const collator = new Intl.Collator('en-US');
console.log(collator.compare('a', 'c')); // -1 (or negative)
console.log(collator.compare('c', 'a')); // 1 (or positive)
console.log(collator.compare('a', 'a')); // 0
```

## 2. Sorting Arrays

This is the most common use case. Instead of the default ASCII sort, you can use a collator for correct alphabetical sorting.

```javascript
const names = ['Zebra', 'Álvaro', 'Aaron', 'älg'];

// Default sort (ASCII based)
console.log([...names].sort()); 
// ["Aaron", "Zebra", "älg", "Álvaro"] (Incorrect for many languages)

// Collator sort
const collator = new Intl.Collator('sv'); // Swedish
console.log([...names].sort(collator.compare));
// ["Aaron", "Zebra", "Álvaro", "älg"] (Correct in Swedish)

const germanCollator = new Intl.Collator('de');
console.log([...names].sort(germanCollator.compare));
// ["Aaron", "älg", "Álvaro", "Zebra"] (Correct in German)
```

## 3. Numeric Sorting

When sorting strings that contain numbers (like filenames), standard sorting can be annoying ("1", "10", "2"). `Intl.Collator` handles this with the `numeric` option.

```javascript
const files = ['file10.txt', 'file2.txt', 'file1.txt'];

// Standard sort
console.log(files.sort()); 
// ["file1.txt", "file10.txt", "file2.txt"]

// Numeric Collator
const numericCollator = new Intl.Collator(undefined, { numeric: true });
console.log(files.sort(numericCollator.compare));
// ["file1.txt", "file2.txt", "file10.txt"]
```

## 4. Sensitivity

You can control how differences in case or accents are treated.

*   `base`: Only strings that differ in base letters compare as unequal. (a == A == á)
*   `accent`: Only strings that differ in base letters or accents and other diacritic marks compare as unequal. (a == A != á)
*   `case`: Only strings that differ in base letters or case compare as unequal. (a != A, a == á)
*   `variant`: Strings that differ in base letters, accents and other diacritic marks, or case compare as unequal. (default)

[[programming/javascript/vanilla/javascript]]
[[programming/javascript/vanilla/intl-numberformat]]
[[programming/javascript/vanilla/intl-datetimeformat]]