# Intl.Segmenter

The `Intl.Segmenter` object enables locale-sensitive text segmentation. It allows you to split a string into meaningful segments, such as graphemes (user-perceived characters), words, or sentences.

## 1. The Problem with `split()`

Traditionally, developers used `string.split(' ')` to count words or split sentences. However, this fails for languages that don't use spaces (like Japanese or Chinese) or for complex emojis that are made of multiple code points.

```javascript
const str = "👨‍👩‍👧‍👦";
console.log(str.length); // 11 (It's actually 4 code points joined by ZWJ)
console.log([...str].length); // 7 (Still not 1 user-perceived character)
```

## 2. Basic Usage

The constructor takes `locales` and `options`. The `segment()` method returns an iterable of segments.

```javascript
const segmenter = new Intl.Segmenter('en', { granularity: 'grapheme' });
const segments = segmenter.segment("👨‍👩‍👧‍👦");

for (const { segment, index, input } of segments) {
  console.log(segment); // "👨‍👩‍👧‍👦" (Correctly identified as 1 grapheme)
}
```

## 3. Granularity

The `granularity` option determines how the string is split.

*   `grapheme`: Split by user-perceived characters (default).
*   `word`: Split by words.
*   `sentence`: Split by sentences.

### Word Segmentation

```javascript
const text = "Hello, world! How are you?";
const wordSegmenter = new Intl.Segmenter('en', { granularity: 'word' });

for (const seg of wordSegmenter.segment(text)) {
  console.log(`'${seg.segment}' (isWordLike: ${seg.isWordLike})`);
}
/* Output:
'Hello' (isWordLike: true)
',' (isWordLike: false)
' ' (isWordLike: false)
'world' (isWordLike: true)
...
*/
```

### Sentence Segmentation

```javascript
const paragraph = "Hello world. This is a test! Is it working?";
const sentenceSegmenter = new Intl.Segmenter('en', { granularity: 'sentence' });

for (const seg of sentenceSegmenter.segment(paragraph)) {
  console.log(seg.segment);
}
```

## 4. Handling Languages without Spaces

`Intl.Segmenter` is essential for languages like Japanese.

```javascript
const japaneseText = "吾輩は猫である";
const segmenter = new Intl.Segmenter('ja', { granularity: 'word' });

const words = [...segmenter.segment(japaneseText)].filter(s => s.isWordLike).map(s => s.segment);
console.log(words); // ["吾輩", "は", "猫", "で", "ある"]
```

[[programming/javascript/vanilla/javascript]]
[[programming/javascript/vanilla/intl-collator]]