Function stringWidthJavaScript

src/ink/stringWidth.ts:20–90

* Fallback JavaScript implementation of stringWidth when Bun.stringWidth is not available. * * Get the display width of a string as it would appear in a terminal. * * This is a more accurate alternative to the string-width package that correctly handles * characters like ⚠ (U+26A0) which string

(str: string)

 * recommended by the Unicode standard for Western contexts.
 */
function stringWidthJavaScript(str: string): number {
  if (typeof str !== 'string' || str.length === 0) {
    return 0
  }

  // Fast path: pure ASCII string (no ANSI codes, no wide chars)
  let isPureAscii = true
  for (let i = 0; i < str.length; i++) {
    const code = str.charCodeAt(i)
    // Check for non-ASCII or ANSI escape (0x1b)
    if (code >= 127 || code === 0x1b) {
      isPureAscii = false
      break
    }
  }
  if (isPureAscii) {
    // Count printable characters (exclude control chars)
    let width = 0
    for (let i = 0; i < str.length; i++) {
      const code = str.charCodeAt(i)
      if (code > 0x1f) {
        width++
      }
    }
    return width
  }

  // Strip ANSI if escape character is present
  if (str.includes('\x1b')) {
    str = stripAnsi(str)
    if (str.length === 0) {
      return 0
    }
  }

  // Fast path: simple Unicode (no emoji, variation selectors, or joiners)
  if (!needsSegmentation(str)) {
    let width = 0
    for (const char of str) {
      const codePoint = char.codePointAt(0)!
      if (!isZeroWidth(codePoint)) {
        width += eastAsianWidth(codePoint, { ambiguousAsWide: false })
      }
    }
    return width
  }

  let width = 0

  for (const { segment: grapheme } of getGraphemeSegmenter().segment(str)) {
    // Check for emoji first (most emoji sequences are width 2)
    EMOJI_REGEX.lastIndex = 0
    if (EMOJI_REGEX.test(grapheme)) {
      width += getEmojiWidth(grapheme)
      continue
    }

    // Calculate width for non-emoji graphemes