perf: increase loader performance by avoiding re-parsing regexps

Author: bhovhannes

index.js

@@ -4,6 +4,13 @@
  */
 var loaderUtils = require('loader-utils');
 
+var REGEX_STYLE = /<style[\s\S]*?>[\s\S]*?<\/style>/i
+var REGEX_DECLARATION = /^\s*<\?xml [^>]*>\s*/i
+
+var REGEX_DOUBLE_QUOTE = /"/g
+var REGEX_MULTIPLE_SPACES = /\s+/g
+var REGEX_UNSAFE_CHARS = /[{}\|\\\^~\[\]`"<>#%]/g
+
 module.exports = function(content) {
 this.cacheable && this.cacheable();
 
@@ -15,10 +22,10 @@ module.exports = function(content) {
 if (limit <= 0 || content.length < limit) {
 var newContent = content.toString('utf8');
 
-var hasStyleElement = /<style[\s\S]*?>[\s\S]*?<\/style>/i.test(newContent)
+var hasStyleElement = REGEX_STYLE.test(newContent)
 
 if (query.stripdeclarations) {
-newContent = newContent.replace(/^\s*<\?xml [^>]*>\s*/i, "");
+newContent = newContent.replace(REGEX_DECLARATION, "");
 }
 
 var data;
@@ -28,9 +35,9 @@ module.exports = function(content) {
 }
 data = "data:image/svg+xml;base64," + newContent.toString("base64");
 } else {
-newContent = newContent.replace(/"/g, "'");
-newContent = newContent.replace(/\s+/g, " ");
-newContent = newContent.replace(/[{}\|\\\^~\[\]`"<>#%]/g, function(match) {
+newContent = newContent.replace(REGEX_DOUBLE_QUOTE, "'");
+newContent = newContent.replace(REGEX_MULTIPLE_SPACES, " ");
+newContent = newContent.replace(REGEX_UNSAFE_CHARS, function(match) {
 return '%'+match[0].charCodeAt(0).toString(16).toUpperCase();
 });