Styled Text Ranges

Requirements

• Export sliceStyledText(input, start, end?) as named and default. input contains text and ranges; each range has start, end, and a string style label. Return a new { text, ranges } object.
• Ranges use half-open UTF-16 offsets [start, end), so end is excluded. Input ranges are valid nonempty ranges inside the original text; overlapping ranges and arbitrary range order are allowed.
• start and end are finite integers with String.slice-style normalization: negative values count from the end, values clamp to the text boundaries, and omitted end means text.length. If normalized end is at or before start, return empty text and ranges.
• Keep every range that intersects the slice. Clip it to the selected interval, then subtract the normalized start to make offsets relative to the new text. Exclude zero-length intersections.
• Preserve original range order, style labels, overlaps, and adjacent equal styles; do not merge, sort, or deduplicate. Every retained range is a new object, even for a full slice.
• Do not mutate input text, ranges, or range objects. Ranges refer to UTF-16 code units, matching JavaScript string indexing; grapheme-aware slicing, validation of malformed ranges, CSS rendering, and rich-text editor UI are outside scope.

Examples

Input: sliceStyledText({ text: "Hello world", ranges: [{ start: 0, end: 5, style: "bold" }] }, 2, 8);
Output: { text: "llo wo", ranges: [{ start: 0, end: 3, style: "bold" }] }

Input: sliceStyledText({ text: "abcdef", ranges: [{ start: 2, end: 6, style: "italic" }] }, -3);
Output: { text: "def", ranges: [{ start: 0, end: 3, style: "italic" }] }