saven/packages/saven-router/src/lib/resolvePathname.js

no

function isAbsolute (pathname) {
  return pathname.charAt(0) === '/'
}

// About 1.5x faster than the two-arg version of Array#splice()
function spliceOne (list, index) {
  for (let i = index, k = i + 1, n = list.length; k < n; i += 1, k += 1) {
    list[i] = list[k]
  }

  list.pop()
}

// This implementation is based heavily on node's url.parse
function resolvePathname (to, from = '') {
  const toParts = (to && to.split('/')) || []
  let fromParts = (from && from.split('/')) || []

  const isToAbs = to && isAbsolute(to)
  const isFromAbs = from && isAbsolute(from)
  const mustEndAbs = isToAbs || isFromAbs

  if (to && isAbsolute(to)) {
    // to is absolute
    fromParts = toParts
  } else if (toParts.length) {
    // to is relative, drop the filename
    fromParts.pop()
    fromParts = fromParts.concat(toParts)
  }

  if (!fromParts.length) {
    return '/'
  }

  let hasTrailingSlash
  if (fromParts.length) {
    const last = fromParts[fromParts.length - 1]
    hasTrailingSlash = last === '.' || last === '..' || last === ''
  } else {
    hasTrailingSlash = false
  }

  let up = 0
  for (let i = fromParts.length; i >= 0; i--) {
    const part = fromParts[i]

    if (part === '.') {
      spliceOne(fromParts, i)
    } else if (part === '..') {
      spliceOne(fromParts, i)
      up++
    } else if (up) {
      spliceOne(fromParts, i)
      up--
    }
  }

  if (!mustEndAbs) {
    for (; up--; up) {
      fromParts.unshift('..')
    }
  }

  if (mustEndAbs && fromParts[0] !== '' && (!fromParts[0] || !isAbsolute(fromParts[0]))) {
    fromParts.unshift('')
  }

  let result = fromParts.join('/')

  if (hasTrailingSlash && result.substr(-1) !== '/') {
    result += '/'
  }

  return result
}

export default resolvePathname