refactor: optimize script execution time

Author: gajus

src/getClassName.js

@@ -6,49 +6,53 @@ import type {
 } from './types';
 
 const isNamespacedStyleName = (styleName: string): boolean => {
-  return styleName.includes('.');
+  return styleName.indexOf('.') !== -1;
 };
 
 const getClassNameForNamespacedStyleName = (styleName: string, styleModuleImportMap: StyleModuleImportMapType): string => {
-  const [
-    importName,
-    moduleName
-  ] = styleName.split('.');
+  // Note:
+  // Do not use the desctructing syntax with Babel.
+  // Desctructing adds _slicedToArray helper.
+  const styleNameParts = styleName.split('.');
+  const importName = styleNameParts[0];
+  const moduleName = styleNameParts[1];
 
   if (!moduleName) {
     throw new Error('Invalid style name.');
   }
 
-  if (!styleModuleImportMap.hasOwnProperty(importName)) {
+  if (!styleModuleImportMap[importName]) {
     throw new Error('Import does not exist.');
   }
 
-  if (!styleModuleImportMap[importName].hasOwnProperty(moduleName)) {
+  if (!styleModuleImportMap[importName][moduleName]) {
     throw new Error('Module does not exist.');
   }
 
   return styleModuleImportMap[importName][moduleName];
 };
 
 export default (styleNameValue: string, styleModuleImportMap: StyleModuleImportMapType): string => {
+  const styleModuleImportMapKeys = Object.keys(styleModuleImportMap);
+
   return styleNameValue
     .split(' ')
     .map((styleName) => {
       if (isNamespacedStyleName(styleName)) {
         return getClassNameForNamespacedStyleName(styleName, styleModuleImportMap);
       }
 
-      if (Object.keys(styleModuleImportMap).length === 0) {
+      if (styleModuleImportMapKeys.length === 0) {
         throw new Error('Cannot use styleName attribute without importing at least one stylesheet.');
       }
 
-      if (Object.keys(styleModuleImportMap).length > 1) {
+      if (styleModuleImportMapKeys.length > 1) {
         throw new Error('Cannot use anonymous style name with more than one stylesheet import.');
       }
 
-      const styleModuleMap: StyleModuleMapType = styleModuleImportMap[Object.keys(styleModuleImportMap)[0]];
+      const styleModuleMap: StyleModuleMapType = styleModuleImportMap[styleModuleImportMapKeys[0]];
 
-      if (!styleModuleMap.hasOwnProperty(styleName)) {
+      if (!styleModuleMap[styleName]) {
         throw new Error('Module cannot be resolved.');
       }