diff --git a/lib/map.js b/lib/map.js
index 7f6d188..6913e9c 100644
--- a/lib/map.js
+++ b/lib/map.js
@@ -1,5 +1,19 @@
 'use strict';
 
-module.exports = function(options) {
-
+module.exports = function(locale, options) {
+  var regexs = {};
+  for (var findString in options.dictionary) {
+    //don't replace characters inside html tags (between `<` and `>`)
+    regexs[options.dictionary[findString]] = new RegExp('(?![^<]*>)' + escapeRegExp(findString), 'g');
+  }
+  for (var hash in locale) {
+    for (var replacement in regexs) {
+      locale[hash] = locale[hash].replace(regexs[replacement], replacement);
+    }
+  }
+  return locale;
 };
+
+function escapeRegExp(string) {
+  return string.replace(/([.*+?^=!:${}()|\[\]\/\\])/g, '\\$1');
+}
diff --git a/test/spec.map.js b/test/spec.map.js
index 6e37e61..bc196fc 100644
--- a/test/spec.map.js
+++ b/test/spec.map.js
@@ -10,8 +10,21 @@ describe('s18n.map()', function() {
     assert.equal(typeof s18n.map, 'function');
   });
 
-  it('should be called', function() {
-    s18n.map();
+  it('should replace substrings using a provided dictionary', function() {
+    var locale = {
+      '3c82f755': 'This is a test.'
+    };
+    var mappedLocale = s18n.map(locale, {
+      dictionary: {
+        'Th': 'Z',
+        'a': 'á',
+        'e': 'é',
+        'i': 'í'
+      }
+    });
+    assert.deepEqual(mappedLocale, {
+      '3c82f755': 'Zís ís á tést.'
+    });
   });
 
 });