refactor: use cache for blogDatas generation

lib/core/index.js

@@ -17,8 +17,8 @@ class App extends React.Component {
           <div>
             {blogDatas.map(({path}) => {
               return (
-                <div>
+                <div key={path}>
-                  <Link key={path} to={path}>
+                  <Link to={path}>
                     {path}
                   </Link>
                 </div>

lib/helpers/generate.js

@@ -0,0 +1,14 @@
+const path = require('path');
+const fs = require('fs-extra');
+
+const genPath = path.resolve(__dirname, '../generated');
+fs.ensureDirSync(genPath);
+
+const genCache = new Map();
+module.exports = async function(file, content) {
+  const cached = genCache.get(file);
+  if (cached !== content) {
+    await fs.writeFile(path.join(genPath, file), content);
+    genCache.set(file, content);
+  }
+};

lib/helpers/index.js

@@ -0,0 +1 @@
+exports.generate = require('./generate');

lib/loader/index.js

@@ -2,6 +2,7 @@ const fs = require('fs-extra');
 const path = require('path');
 const loadConfig = require('./config');
 const loadBlog = require('./blog');
+const {generate} = require('../helpers');
 
 module.exports = async function load(sourceDir) {
   // load siteConfig
@@ -10,13 +11,13 @@ module.exports = async function load(sourceDir) {
   // extract data from all blog files
   const blogDatas = await loadBlog(sourceDir);
 
-  fs.writeFile(
+  await generate(
-    path.resolve(__dirname, '../generated/blogDatas.js'),
+    'blogDatas.js',
-    `${'/**\n' +
+    `${'/**\n * @generated\n */\n' + 'module.exports = '}${JSON.stringify(
-    ' * @' +
+      blogDatas,
-    'generated\n' +
+      null,
-      ' */\n' +
+      2
-      'module.exports = '}${JSON.stringify(blogDatas, null, 2)};\n`
+    )};\n`
   );
 
   // resolve outDir