ECMAScript Intl.Segmenter Proposal

Create a new locale-dependent segmenter using new Intl.Segmenter(locale, options). The options object allows you to specify the granularity of the segmentation.

Supported granularity values:

• "grapheme" (default): Finds boundaries between user-perceived characters.
• "word": Finds boundaries between words and non-word characters (like spaces or punctuation).
• "sentence": Finds boundaries between sentences.

// Create a locale-specific word segmenter
let segmenter = new Intl.Segmenter("fr", {granularity: "word"});

Use the segment(string) method on an Intl.Segmenter instance to produce a %Segments% object. This object is an iterable that can be used in a for...of loop to access individual segments.

Each segment is a plain object containing:

• segment: The actual string segment.
• index: The starting code unit index in the original string.
• input: The original input string.
• isWordLike: (Only when granularity is "word") true if the segment consists of letters/numbers/ideographs, false if it is whitespace/punctuation, and undefined otherwise.

let segmenter = new Intl.Segmenter("fr", {granularity: "word"});
let input = "Moi?  N'est-ce pas.";
let segments = segmenter.segment(input);

for (let {segment, index, isWordLike} of segments) {
  console.log(segment, index, isWordLike);
}

The %Segments% object provides a containing(index) method for direct random access. This allows you to find the specific segment that encompasses a given code unit index without iterating from the beginning.

• If the index is within a segment, it returns that segment's data object.
• If the index is out of bounds, it returns undefined.
• The index argument is coerced into an integer (e.g., null or NaN becomes 0).

let input = "Allons-y!";
let segmenter = new Intl.Segmenter("fr", {granularity: "word"});
let segments = segmenter.segment(input);

// Returns the segment containing the character at index 0
let current = segments.containing(0);
// → { index: 0, segment: "Allons", isWordLike: true }

// Returns the segment containing the character at index 6
current = segments.containing(6);
// → { index: 6, segment: "-", isWordLike: false }

When iterating or using containing(), the returned segment data follows this schema: