1 files changed, 75 insertions, 0 deletions
diff --git a/resolve-pathname/modules/index.js b/resolve-pathname/modules/index.js
new file mode 100644
index 0000000..77afb3e
--- /dev/null
+++ b/resolve-pathname/modules/index.js
@@ -0,0 +1,75 @@
+function isAbsolute(pathname) {
+  return pathname.charAt(0) === '/';
+}
+
+// About 1.5x faster than the two-arg version of Array#splice()
+function spliceOne(list, index) {
+  for (var 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) {
+  if (from === undefined) from = '';
+
+  var toParts = (to && to.split('/')) || [];
+  var fromParts = (from && from.split('/')) || [];
+
+  var isToAbs = to && isAbsolute(to);
+  var isFromAbs = from && isAbsolute(from);
+  var 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 '/';
+
+  var hasTrailingSlash;
+  if (fromParts.length) {
+    var last = fromParts[fromParts.length - 1];
+    hasTrailingSlash = last === '.' || last === '..' || last === '';
+  } else {
+    hasTrailingSlash = false;
+  }
+
+  var up = 0;
+  for (var i = fromParts.length; i >= 0; i--) {
+    var 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('');
+
+  var result = fromParts.join('/');
+
+  if (hasTrailingSlash && result.substr(-1) !== '/') result += '/';
+
+  return result;
+}
+
+export default resolvePathname;