diff --git a/index.js b/index.js
index 98013d1..6037809 100644
--- a/index.js
+++ b/index.js
@@ -22,16 +22,16 @@ function retrieveFile(path) {
   }
 
   if (/^\S+:\/\//.test(path) && !/^http(s)?:\/\//.test(path)) {
-    return null
+    return null;
   }
 
   try {
     var xhr = new XMLHttpRequest();
     xhr.open('GET', path, false);
     xhr.send(null);
-    var contents = null
+    var contents = null;
     if (xhr.readyState === 4 && xhr.status === 200) {
-      contents = xhr.responseText
+      contents = xhr.responseText;
     }
 
   } catch (e) {
@@ -44,9 +44,11 @@ function retrieveFile(path) {
 // Support URLs relative to a directory, but be careful about a protocol prefix
 // in case we are in the browser (i.e. directories may start with "http://")
 function supportRelativeURL(file, url) {
+  var regx = /^\w+:\/\/[^\/]*/;
+  if (regx.test(url)) return url;
   if (!file) return url;
   var dir = path.dirname(file);
-  var match = /^\w+:\/\/[^\/]*/.exec(dir);
+  var match = regx.exec(dir);
   var protocol = match ? match[0] : '';
   return protocol + path.resolve(dir.slice(protocol.length), url);
 }
@@ -62,12 +64,11 @@ function retrieveSourceMapURL(source, position) {
         fileData = xhr.responseText;
         fileContentsCache[source] = fileData;
       }
-      if (xhr.status !== 200) return null
-    } catch (e) { return null }
+      if (xhr.status !== 200) return null;
+    } catch (e) { return null; }
 
     // Support providing a sourceMappingURL via the SourceMap header
-    var sourceMapHeader = xhr.getResponseHeader('SourceMap') ||
-                          xhr.getResponseHeader('X-SourceMap');
+    var sourceMapHeader = xhr.getResponseHeader('SourceMap') || xhr.getResponseHeader('X-SourceMap');
     if (sourceMapHeader) {
       return sourceMapHeader;
     }
@@ -80,7 +81,7 @@ function retrieveSourceMapURL(source, position) {
   while (match = re.exec(fileData)) lastMatch = match; // eslint-disable-line
   if (!lastMatch) {
     var line = fileData.split(/(?:\r\n|\r|\n)/)[position.line - 1];
-    line = line.replace(/^.*sourceMappingURL=/, '').replace(/"\s*\);\s*$/,'')
+    line = line.replace(/^.*sourceMappingURL=/, '').replace(/"\s*\);\s*$/,'');
     if (reSourceMap.test(line)) return line;
     return null;
   }
@@ -103,8 +104,8 @@ function retrieveSourceMap(source, position) {
     // Support source map URL as a data url
     var rawData = sourceMappingURL.slice(sourceMappingURL.indexOf(',') + 1);
     sourceMapData = new Buffer(rawData, 'base64').toString();
-    sourceMapData = JSON.parse(sourceMapData)
-    source = sourceMapData.sources[0]
+    sourceMapData = JSON.parse(sourceMapData);
+    source = sourceMapData.sources[0];
     sourceMappingURL = null;
   } else {
     // Support source map URLs relative to the source URL
@@ -128,8 +129,8 @@ function mapSourcePosition(position) {
     // Call the (overrideable) retrieveSourceMap function to get the source map.
     var urlAndMap = retrieveSourceMap(position.source, position);
     if (urlAndMap) {
-      var source = urlAndMap.url ? position.source : urlAndMap.map.sources[0]
-      position.source = source
+      var source = urlAndMap.url ? position.source : urlAndMap.map.sources[0];
+      position.source = source;
       sourceMap = sourceMapCache[source] = {
         url: urlAndMap.url,
         map: new SourceMapConsumer(urlAndMap.map)
@@ -156,17 +157,17 @@ function mapSourcePosition(position) {
 
   // Resolve the source URL relative to the URL of the source map
   if (sourceMap && sourceMap.map) {
-    var pos
+    var pos;
     if (position.eval) {
       pos = {
         line: position.eval[0],
         column: position.eval[1]
-      }
+      };
     } else {
       pos = {
         line: position.line,
         column: position.column
-      }
+      };
     }
 
     var originalPosition = sourceMap.map.originalPositionFor(pos);
@@ -200,7 +201,7 @@ function getEvalPosition(origin, ln, cn) {
       eval:[ln, cn]
     });
 
-    return position
+    return position;
   }
 
   // Parse nested eval() calls using recursion
@@ -231,8 +232,8 @@ function CallSiteToString() {
       fileLocation += ', ';  // Expecting source position to follow.
     }
     if (fileName && !/^\w+:\/\//.test(fileName)) {
-      var root = location.protocol + '//' + location.host
-      fileName = root + (/^\//.test(fileName) ? fileName : '/' + fileName)
+      var root = location.protocol + '//' + location.host;
+      fileName = root + (/^\//.test(fileName) ? fileName : '/' + fileName);
     }
 
     if (fileName) {
@@ -299,9 +300,9 @@ function wrapCallSite(frame) {
   // Most call sites will return the source file from getFileName(), but code
   // passed to eval() ending in "//# sourceURL=..." will return the source file
   // from getScriptNameOrSourceURL() instead
-  if (frame.isNative()) return frame
+  if (frame.isNative()) return frame;
   var source = frame.getFileName() || frame.getScriptNameOrSourceURL();
-  var position
+  var position;
   if (source) {
     var line = frame.getLineNumber();
     var column = frame.getColumnNumber() - 1;
@@ -322,15 +323,15 @@ function wrapCallSite(frame) {
   var origin = frame.isEval() && frame.getEvalOrigin();
   if (origin) {
     // ln and cn in eval
-    var ln = frame.getLineNumber()
-    var cn = frame.getColumnNumber()
+    var ln = frame.getLineNumber();
+    var cn = frame.getColumnNumber();
     position = getEvalPosition(origin, ln, cn);
     frame = cloneCallSite(frame);
     frame.getScriptNameOrSourceURL = function() { return position.source.replace(/\?.*$/, ''); };
     frame.getLineNumber = function() { return position.line; };
     frame.getColumnNumber = function() { return position.column ? position.column + 1: cn; };
     frame.getEvalOrigin = function() { return origin; };
-    frame.getFileName = function () { return position.source}
+    frame.getFileName = function () { return position.source;};
     return frame;
   }
 
@@ -347,8 +348,8 @@ function prepareStackTrace(error, stack) {
   }
   stack = stack.filter(function (frame) {
     var source = frame.getFileName() || frame.getScriptNameOrSourceURL();
-    return !/node_modules\/mocha/.test(source)
-  })
+    return !/node_modules\/mocha/.test(source);
+  });
   return error + stack.map(function(frame) {
     return '\n    at ' + wrapCallSite(frame);
   }).join('');
@@ -370,8 +371,7 @@ function getErrorSource(error) {
     if (contents) {
       var code = contents.split(/(?:\r\n|\r|\n)/)[line - 1];
       if (code) {
-        return source + ':' + line + '\n' + code + '\n' +
-          new Array(column).join(' ') + '^';
+        return source + ':' + line + '\n' + code + '\n' + new Array(column).join(' ') + '^';
       }
     }
   }
@@ -384,12 +384,12 @@ exports.mapSourcePosition = mapSourcePosition;
 exports.retrieveSourceMap = retrieveSourceMap;
 
 module.exports = function (option) {
-  option = option || {}
+  option = option || {};
   if (/^file/i.test(location.protocol)) {
-    console.warn('stack-source-map not works on file protocol')
+    console.warn('stack-source-map not works on file protocol');
   } else {
     Error.prepareStackTrace = prepareStackTrace;
   }
-  if (option.hasOwnProperty('empty')) emptyCacheBetweenOperations = option.empty
-}
+  if (option.hasOwnProperty('empty')) emptyCacheBetweenOperations = option.empty;
+};