diff --git a/lib/generate-icon-set-from-css.js b/lib/generate-icon-set-from-css.js
index 399b9e6..2c5ef16 100644
--- a/lib/generate-icon-set-from-css.js
+++ b/lib/generate-icon-set-from-css.js
@@ -1,57 +1,55 @@
-/**
- * @providesModule generateIconSetFromCss
- */
-'use strict';
-var _ = require('lodash');
-var fs = require('fs');
+const _ = require('lodash');
+const fs = require('fs');
 
 function extractGlyphMapFromCss(files, selectorPattern) {
-  var styleRulePattern = '(\\.[A-Za-z0-9_.:, \\n\\t-]+)\\{[^}]*content: ?["\\\'](?:\\\\([A-Fa-f0-9]+)|([^"\\\']+))["\\\'][^}]*\\}';
-  var allStyleRules = new RegExp(styleRulePattern, 'g');
-  var singleStyleRules = new RegExp(styleRulePattern);
-  var allSelectors = new RegExp(selectorPattern, 'g');
-  var singleSelector = new RegExp(selectorPattern);
+  const styleRulePattern = '(\\.[A-Za-z0-9_.:, \\n\\t-]+)\\{[^}]*content: ?["\\\'](?:\\\\([A-Fa-f0-9]+)|([^"\\\']+))["\\\'][^}]*\\}';
+  const allStyleRules = new RegExp(styleRulePattern, 'g');
+  const singleStyleRules = new RegExp(styleRulePattern);
+  const allSelectors = new RegExp(selectorPattern, 'g');
+  const singleSelector = new RegExp(selectorPattern);
 
-  var glyphMap = {};
-  if(typeof files === 'string') {
-    files = [files];
-  }
-
-  files.forEach(function(fileName) {
-    var contents = fs.readFileSync(fileName, { encoding: 'utf8' });
-    var rules = contents.match(allStyleRules);
-    if(rules) {
-      rules.forEach(function(rule) {
-        var ruleParts = rule.match(singleStyleRules);
-        var hexCharCode = ruleParts[2], actualChar = ruleParts[3];
-        var charCode = hexCharCode ? parseInt(hexCharCode, 16) : (actualChar.length > 1 ? actualChar : actualChar.charCodeAt());
-        var selectors = ruleParts[1].match(allSelectors);
-        if(selectors) {
-          selectors.forEach(function(selector) {
-            var name = selector.match(singleSelector)[1];
-            glyphMap[name] = charCode;
-          });
-        }
-      });
+  const extractGlyphFromRule = (rule) => {
+    const ruleParts = rule.match(singleStyleRules);
+    if (ruleParts[2]) {
+      // Hex value in CSS
+      return parseInt(ruleParts[2], 16);
+    } else if (ruleParts[3].length > 1) {
+      // String value in CSS that we'll keep as a string because it's not a single character
+      return ruleParts[3];
     }
-  });
-  return glyphMap;
-};
+    // String value in CSS that we'll convert to a charcode
+    return ruleParts[3].charCodeAt();
+  };
 
-function escapeRegExp(str) {
-  return str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&");
+  const extractSelectorsFromRule = (rule) => {
+    const ruleParts = rule.match(singleStyleRules);
+    const selectors = ruleParts[1].match(allSelectors) || [];
+    return selectors.map(selector => selector.match(singleSelector)[1]);
+  };
+
+  return (typeof files === 'string' ? [files] : files)
+    .map(fileName => fs.readFileSync(fileName, { encoding: 'utf8' }))
+    .map(contents => contents.match(allStyleRules) || [])
+    .reduce((acc, rules) => acc.concat(rules), [])
+    .map((rule) => {
+      const glyph = extractGlyphFromRule(rule);
+      const selectors = extractSelectorsFromRule(rule);
+      return selectors.map(selector => [selector, glyph]);
+    })
+    .reduce((acc, glyphs) => Object.assign(acc, _.fromPairs(glyphs)), {});
 }
 
-function generateIconSetFromCss(cssFiles, selectorPrefix, template, data) {
-  var glyphMap = extractGlyphMapFromCss(cssFiles, escapeRegExp(selectorPrefix) + '([A-Za-z0-9_-]+):before');
-  var content = JSON.stringify(glyphMap, null, '  ');
-  if(template) {
-    var compiled = _.template(template);
-    data = data || {};
-    data.glyphMap = content;
-    content = compiled(data);
+function escapeRegExp(str) {
+  return str.replace(/[-[\]/{}()*+?.\\^$|]/g, '\\$&');
+}
+
+function generateIconSetFromCss(cssFiles, selectorPrefix, template, data = {}) {
+  const glyphMap = extractGlyphMapFromCss(cssFiles, `${escapeRegExp(selectorPrefix)}([A-Za-z0-9_-]+):before`);
+  const content = JSON.stringify(glyphMap, null, '  ');
+  if (template) {
+    return _.template(template)(Object.assign({ glyphMap: content }, data));
   }
   return content;
-};
+}
 
 module.exports = generateIconSetFromCss;