function utf8ToBytes()

in src/aws-client.js [16564:16642]
60 lines of code
22 McCabe index (conditional complexity)

  function utf8ToBytes (string, units) {
    units = units || Infinity
    var codePoint
    var length = string.length
    var leadSurrogate = null
    var bytes = []
  
    for (var i = 0; i < length; ++i) {
      codePoint = string.charCodeAt(i)
  
      // is surrogate component
      if (codePoint > 0xD7FF && codePoint < 0xE000) {
        // last char was a lead
        if (!leadSurrogate) {
          // no lead yet
          if (codePoint > 0xDBFF) {
            // unexpected trail
            if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
            continue
          } else if (i + 1 === length) {
            // unpaired lead
            if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
            continue
          }
  
          // valid lead
          leadSurrogate = codePoint
  
          continue
        }
  
        // 2 leads in a row
        if (codePoint < 0xDC00) {
          if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
          leadSurrogate = codePoint
          continue
        }
  
        // valid surrogate pair
        codePoint = (leadSurrogate - 0xD800 << 10 | codePoint - 0xDC00) + 0x10000
      } else if (leadSurrogate) {
        // valid bmp char, but last char was a lead
        if ((units -= 3) > -1) bytes.push(0xEF, 0xBF, 0xBD)
      }
  
      leadSurrogate = null
  
      // encode utf8
      if (codePoint < 0x80) {
        if ((units -= 1) < 0) break
        bytes.push(codePoint)
      } else if (codePoint < 0x800) {
        if ((units -= 2) < 0) break
        bytes.push(
          codePoint >> 0x6 | 0xC0,
          codePoint & 0x3F | 0x80
        )
      } else if (codePoint < 0x10000) {
        if ((units -= 3) < 0) break
        bytes.push(
          codePoint >> 0xC | 0xE0,
          codePoint >> 0x6 & 0x3F | 0x80,
          codePoint & 0x3F | 0x80
        )
      } else if (codePoint < 0x110000) {
        if ((units -= 4) < 0) break
        bytes.push(
          codePoint >> 0x12 | 0xF0,
          codePoint >> 0xC & 0x3F | 0x80,
          codePoint >> 0x6 & 0x3F | 0x80,
          codePoint & 0x3F | 0x80
        )
      } else {
        throw new Error('Invalid code point')
      }
    }
  
    return bytes
  }