resolve-url.js

// Copyright 2014 Simon Lydell
// X11 (“MIT”) Licensed. (See LICENSE.)

void (function(root, factory) {
  if (typeof define === "function" && define.amd) {
    define(factory)
  } else if (typeof exports === "object") {
    module.exports = factory()
  } else {
    root.resolveUrl = factory()
  }
}(this, function() {

  function resolveUrl(/* ...urls */) {
    var numUrls = arguments.length

    if (numUrls === 0) {
      throw new Error("resolveUrl requires at least one argument; got none.")
    }

    var base = document.createElement("base")
    base.href = arguments[0]

    if (numUrls === 1) {
      return base.href
    }

    var head = document.getElementsByTagName("head")[0]
    head.insertBefore(base, head.firstChild)

    var a = document.createElement("a")
    var resolved

    for (var index = 1; index < numUrls; index++) {
      a.href = arguments[index]
      resolved = a.href
      base.href = resolved
    }

    head.removeChild(base)

    return resolved
  }

  return resolveUrl

}));