diff --git a/src/ui/js/diff2html-ui.js b/src/ui/js/diff2html-ui.js
index fb18f2b..5b4daa4 100644
--- a/src/ui/js/diff2html-ui.js
+++ b/src/ui/js/diff2html-ui.js
@@ -12,6 +12,8 @@
 
 (function() {
 
+  var highlightJS = require('./highlight.js-internals.js').HighlightJS;
+
   var diffJson = null;
   var defaultTarget = "body";
   var currentSelectionColumnId = -1;
@@ -71,7 +73,7 @@
 
     // collect all the diff files and execute the highlight on their lines
     var $files = $target.find(".d2h-file-wrapper");
-    $files.map(function(i, file) {
+    $files.map(function(_i, file) {
       var oldLinesState;
       var newLinesState;
       var $file = $(file);
@@ -79,7 +81,7 @@
 
       // collect all the code lines and execute the highlight on them
       var $codeLines = $file.find(".d2h-code-line-ctn");
-      $codeLines.map(function(i, line) {
+      $codeLines.map(function(_j, line) {
         var $line = $(line);
         var text = line.textContent;
         var lineParent = line.parentNode;
@@ -102,11 +104,11 @@
           newLinesState = result.top;
         }
 
-        var originalStream = nodeStream(line);
+        var originalStream = highlightJS.nodeStream(line);
         if (originalStream.length) {
           var resultNode = document.createElementNS('http://www.w3.org/1999/xhtml', 'div');
           resultNode.innerHTML = result.value;
-          result.value = mergeStreams(originalStream, nodeStream(resultNode), text);
+          result.value = highlightJS.mergeStreams(originalStream, highlightJS.nodeStream(resultNode), text);
         }
 
         $line.addClass("hljs");
@@ -198,129 +200,6 @@
     return text;
   };
 
-  /*
-   * Copied from Highlight.js Private API
-   * Will be removed when this part of the API is exposed
-   */
-
-  /* Utility functions */
-
-  function escape(value) {
-    return value.replace(/&/gm, '&amp;').replace(/</gm, '&lt;').replace(/>/gm, '&gt;');
-  }
-
-  function tag(node) {
-    return node.nodeName.toLowerCase();
-  }
-
-  /* Stream merging */
-
-  function nodeStream(node) {
-    var result = [];
-    (function _nodeStream(node, offset) {
-      for (var child = node.firstChild; child; child = child.nextSibling) {
-        if (child.nodeType == 3)
-          offset += child.nodeValue.length;
-        else if (child.nodeType == 1) {
-          result.push({
-            event: 'start',
-            offset: offset,
-            node: child
-          });
-          offset = _nodeStream(child, offset);
-          // Prevent void elements from having an end tag that would actually
-          // double them in the output. There are more void elements in HTML
-          // but we list only those realistically expected in code display.
-          if (!tag(child).match(/br|hr|img|input/)) {
-            result.push({
-              event: 'stop',
-              offset: offset,
-              node: child
-            });
-          }
-        }
-      }
-      return offset;
-    })(node, 0);
-    return result;
-  }
-
-  function mergeStreams(original, highlighted, value) {
-    var processed = 0;
-    var result = '';
-    var nodeStack = [];
-
-    function selectStream() {
-      if (!original.length || !highlighted.length) {
-        return original.length ? original : highlighted;
-      }
-      if (original[0].offset != highlighted[0].offset) {
-        return (original[0].offset < highlighted[0].offset) ? original : highlighted;
-      }
-
-      /*
-       To avoid starting the stream just before it should stop the order is
-       ensured that original always starts first and closes last:
-       if (event1 == 'start' && event2 == 'start')
-       return original;
-       if (event1 == 'start' && event2 == 'stop')
-       return highlighted;
-       if (event1 == 'stop' && event2 == 'start')
-       return original;
-       if (event1 == 'stop' && event2 == 'stop')
-       return highlighted;
-       ... which is collapsed to:
-       */
-      return highlighted[0].event == 'start' ? original : highlighted;
-    }
-
-    function open(node) {
-      function attrStr(a) {
-        return ' ' + a.nodeName + '="' + escape(a.value) + '"';
-      }
-
-      result += '<' + tag(node) + Array.prototype.map.call(node.attributes, attrStr).join('') + '>';
-    }
-
-    function close(node) {
-      result += '</' + tag(node) + '>';
-    }
-
-    function render(event) {
-      (event.event == 'start' ? open : close)(event.node);
-    }
-
-    while (original.length || highlighted.length) {
-      var stream = selectStream();
-      result += escape(value.substr(processed, stream[0].offset - processed));
-      processed = stream[0].offset;
-      if (stream == original) {
-        /*
-         On any opening or closing tag of the original markup we first close
-         the entire highlighted node stack, then render the original tag along
-         with all the following original tags at the same offset and then
-         reopen all the tags on the highlighted stack.
-         */
-        nodeStack.reverse().forEach(close);
-        do {
-          render(stream.splice(0, 1)[0]);
-          stream = selectStream();
-        } while (stream == original && stream.length && stream[0].offset == processed);
-        nodeStack.reverse().forEach(open);
-      } else {
-        if (stream[0].event == 'start') {
-          nodeStack.push(stream[0].node);
-        } else {
-          nodeStack.pop();
-        }
-        render(stream.splice(0, 1)[0]);
-      }
-    }
-    return result + escape(value.substr(processed));
-  }
-
-  /* **** Highlight.js Private API **** */
-
   module.exports.Diff2HtmlUI = Diff2HtmlUI;
 
   // Expose diff2html in the browser
diff --git a/src/ui/js/highlight.js-internals.js b/src/ui/js/highlight.js-internals.js
new file mode 100644
index 0000000..8bac6b4
--- /dev/null
+++ b/src/ui/js/highlight.js-internals.js
@@ -0,0 +1,139 @@
+/*
+ *
+ * highlight.js
+ * Author: isagalaev
+ *
+ */
+
+(function() {
+
+  function HighlightJS() {
+  }
+
+  /*
+   * Copied from Highlight.js Private API
+   * Will be removed when this part of the API is exposed
+   */
+
+  /* Utility functions */
+
+  function escape(value) {
+    return value.replace(/&/gm, '&amp;').replace(/</gm, '&lt;').replace(/>/gm, '&gt;');
+  }
+
+  function tag(node) {
+    return node.nodeName.toLowerCase();
+  }
+
+  /* Stream merging */
+
+  HighlightJS.prototype.nodeStream = function(node) {
+    var result = [];
+    (function _nodeStream(node, offset) {
+      for (var child = node.firstChild; child; child = child.nextSibling) {
+        if (child.nodeType == 3)
+          offset += child.nodeValue.length;
+        else if (child.nodeType == 1) {
+          result.push({
+            event: 'start',
+            offset: offset,
+            node: child
+          });
+          offset = _nodeStream(child, offset);
+          // Prevent void elements from having an end tag that would actually
+          // double them in the output. There are more void elements in HTML
+          // but we list only those realistically expected in code display.
+          if (!tag(child).match(/br|hr|img|input/)) {
+            result.push({
+              event: 'stop',
+              offset: offset,
+              node: child
+            });
+          }
+        }
+      }
+      return offset;
+    })(node, 0);
+    return result;
+  };
+
+  HighlightJS.prototype.mergeStreams = function(original, highlighted, value) {
+    var processed = 0;
+    var result = '';
+    var nodeStack = [];
+
+    function selectStream() {
+      if (!original.length || !highlighted.length) {
+        return original.length ? original : highlighted;
+      }
+      if (original[0].offset != highlighted[0].offset) {
+        return (original[0].offset < highlighted[0].offset) ? original : highlighted;
+      }
+
+      /*
+       To avoid starting the stream just before it should stop the order is
+       ensured that original always starts first and closes last:
+       if (event1 == 'start' && event2 == 'start')
+       return original;
+       if (event1 == 'start' && event2 == 'stop')
+       return highlighted;
+       if (event1 == 'stop' && event2 == 'start')
+       return original;
+       if (event1 == 'stop' && event2 == 'stop')
+       return highlighted;
+       ... which is collapsed to:
+       */
+      return highlighted[0].event == 'start' ? original : highlighted;
+    }
+
+    function open(node) {
+      function attrStr(a) {
+        return ' ' + a.nodeName + '="' + escape(a.value) + '"';
+      }
+
+      result += '<' + tag(node) + Array.prototype.map.call(node.attributes, attrStr).join('') + '>';
+    }
+
+    function close(node) {
+      result += '</' + tag(node) + '>';
+    }
+
+    function render(event) {
+      (event.event == 'start' ? open : close)(event.node);
+    }
+
+    while (original.length || highlighted.length) {
+      var stream = selectStream();
+      result += escape(value.substr(processed, stream[0].offset - processed));
+      processed = stream[0].offset;
+      if (stream == original) {
+
+        /*
+         On any opening or closing tag of the original markup we first close
+         the entire highlighted node stack, then render the original tag along
+         with all the following original tags at the same offset and then
+         reopen all the tags on the highlighted stack.
+         */
+        nodeStack.reverse().forEach(close);
+        do {
+          render(stream.splice(0, 1)[0]);
+          stream = selectStream();
+        } while (stream == original && stream.length && stream[0].offset == processed);
+        nodeStack.reverse().forEach(open);
+      } else {
+        if (stream[0].event == 'start') {
+          nodeStack.push(stream[0].node);
+        } else {
+          nodeStack.pop();
+        }
+        render(stream.splice(0, 1)[0]);
+      }
+    }
+    return result + escape(value.substr(processed));
+  };
+
+  /* **** Highlight.js Private API **** */
+
+  module.exports.HighlightJS = new HighlightJS();
+
+})();