Passes all the tests with these changes.

lib/url-join.js

@@ -8,26 +8,49 @@
     return str.substr(0, searchString.length) === searchString;
   }
 
-  function normalize (str, options) {
-
-    if (startsWith(str, 'file://')) {
-
-      // make sure file protocol has max three slashes
-      str = str.replace(/(\/{0,3})\/*/g, '$1');
-    } else {
-
-      // make sure protocol is followed by two slashes
-      str = str.replace(/:\//g, '://');
-
-      // remove consecutive slashes
-      str = str.replace(/([^:\s\%\3\A])\/+/g, '$1/');
+  function normalize (strArray, options) {
+    var resultArray = [];
+
+    // If the first part is a plain protocol, we combine it with the next part.
+    if (strArray[0].match(/:\/*$/) && strArray.length > 1) {
+      var first = strArray.shift();
+      strArray[0] = first + strArray[0];
+      // There must be at least two in any, at most three slashes in the file protocol.
+      if (strArray[0].match(/file:\/\/\//)) {
+        strArray[0] = strArray[0].replace(/:\/*/, ':///');
+      } else {
+        strArray[0] = strArray[0].replace(/:\/*/, '://');
+      }
+    }
+
+    for (var i = 0; i < strArray.length; i++) {
+
+      var component = strArray[i];
+      if (i > 0) {
+        // Removing the starting slashes for each component but the first.
+        component = component.replace(/^[\/]+/, '');
+      }
+      if (i < strArray.length - 1) {
+        // Removing the ending slashes for each component but the last.
+        component = component.replace(/[\/]+$/, '');
+      } else {
+        // For the last component we will combine multiple slashes to a single one.
+        component = component.replace(/[\/]+$/, '/');
+      }
+
+      resultArray.push(component);
+
     }
+
+    var str = resultArray.join('/');
+    // Each input component is now separated by a single slash except the possible first plain protocol part.
 
     // remove trailing slash before parameters or hash
     str = str.replace(/\/(\?|&|#[^!])/g, '$1');
 
     // replace ? in parameters with &
-    str = str.replace(/(\?.+)\?/g, '$1&');
+    var parts = str.split('?');
+    str = parts.shift() + (parts.length > 0 ? '?': '') + parts.join('&');
 
     return str;
   }
@@ -41,9 +64,8 @@
       input = arguments[0];
       options = arguments[1] || {};
     }
-
-    var joined = [].slice.call(input, 0).join('/');
-    return normalize(joined, options);
+
+    return normalize([].slice.call(input), options);
   };
 
 });

test/tests.js

@@ -78,11 +78,9 @@ describe('url join', function () {
 
     urljoin('http:', 'www.google.com///', 'foo/bar', '?test=123', '?boom=value', '&key=456')
       .should.eql('http://www.google.com/foo/bar?test=123&boom=value&key=456');
-  });
 
-  it('should merge multiple query params with more than two query params properly', function () {
     urljoin('http://example.org/x', '?a=1', '?b=2', '?c=3', '?d=4')
-      .should.eql('http://example.org/x?a=1&b=2&c=3&d=4');
+    .should.eql('http://example.org/x?a=1&b=2&c=3&d=4');
   });
 
   it('should merge slashes in paths correctly', function () {