Method Split

regex.go:1288–1337

Split slices s into substrings separated by the expression and returns a slice of the substrings between those expression matches. The slice returned by this method consists of all the substrings of s not contained in the slice returned by FindAllString. When called on an expression that contains n

(s string, n int)

//	parts = re.Split("a,b,c", 2)
//	// parts = ["a", "b,c"]
func (r *Regex) Split(s string, n int) []string {
	if n == 0 {
		return nil
	}

	indices := r.FindAllStringIndex(s, -1)
	if len(indices) == 0 {
		// No matches, return entire string
		return []string{s}
	}

	// Determine the number of splits
	numSplits := len(indices) + 1
	if n > 0 && n < numSplits {
		numSplits = n
	}

	// Pre-allocate result slice
	result := make([]string, 0, numSplits)

	lastEnd := 0
	for _, idx := range indices {
		// Skip empty match at the beginning (position 0 with zero-width match)
		// This matches stdlib behavior: Split("", "abc") = ["a", "b", "c"], not ["", "a", "b", "c", ""]
		if lastEnd == 0 && idx[0] == 0 && idx[1] == 0 {
			continue
		}

		// Skip empty match at the very end of string
		if idx[0] == len(s) && idx[1] == len(s) {
			break
		}

		// Add substring before match
		result = append(result, s[lastEnd:idx[0]])
		lastEnd = idx[1]

		// Check if we've reached the limit (but need room for final element)
		if n > 0 && len(result) >= n-1 {
			// Add the rest as the final element
			result = append(result, s[lastEnd:])
			return result
		}
	}

	// Add remaining text after last match
	// Always add even if empty (matches stdlib behavior)
	result = append(result, s[lastEnd:])
	return result
}

// Count returns the number of non-overlapping matches of the pattern in b.
// If n > 0, counts at most n matches. If n <= 0, counts all matches.