code: function parseTokenList (str) {
    var end = 0
    var list = []
    var start = 0
  
    // gather tokens
    for (var i = 0, len = str.length; i < len; i++) {
      switch (str.charCodeAt(i)) {
        case 0x20: /*   */
          if (start === end) {
            start = end = i + 1
          }
          break
        case 0x2c: /* , */
          list.push(str.substring(start, end))
          start = end = i + 1
          break
        default:
          end = i + 1
          break
      }
    }
  
    // final token
    list.push(str.substring(start, end))
  
    return list
  }
docs: Parse a HTTP token list.
  
  @param {string} str
  @private