diff --git a/lib/hexo/render.js b/lib/hexo/render.js
index 40029d46e0..788f4dc153 100644
--- a/lib/hexo/render.js
+++ b/lib/hexo/render.js
@@ -2,127 +2,129 @@
 
 const { extname } = require('path');
 const Promise = require('bluebird');
-const fs = require('hexo-fs');
+const { readFile, readFileSync } = require('hexo-fs');
 
-function getExtname(str) {
+const getExtname = str => {
   if (typeof str !== 'string') return '';
 
   const ext = extname(str);
   return ext[0] === '.' ? ext.slice(1) : ext;
-}
-
-function Render(ctx) {
-  this.context = ctx;
-  this.renderer = ctx.extend.renderer;
-}
-
-Render.prototype.isRenderable = function(path) {
-  return this.renderer.isRenderable(path);
 };
 
-Render.prototype.isRenderableSync = function(path) {
-  return this.renderer.isRenderableSync(path);
-};
-
-Render.prototype.getOutput = function(path) {
-  return this.renderer.getOutput(path);
-};
+const toString = (result, options) => {
+  if (!Object.prototype.hasOwnProperty.call(options, 'toString') || typeof result === 'string') return result;
 
-Render.prototype.getRenderer = function(ext, sync) {
-  return this.renderer.get(ext, sync);
-};
+  if (typeof options.toString === 'function') {
+    return options.toString(result);
+  } else if (typeof result === 'object') {
+    return JSON.stringify(result);
+  } else if (result.toString) {
+    return result.toString();
+  }
 
-Render.prototype.getRendererSync = function(ext) {
-  return this.getRenderer(ext, true);
+  return result;
 };
 
-Render.prototype.render = function(data, options, callback) {
-  if (!callback && typeof options === 'function') {
-    callback = options;
-    options = {};
+class Render {
+  constructor(ctx) {
+    this.context = ctx;
+    this.renderer = ctx.extend.renderer;
   }
 
-  const ctx = this.context;
-  let ext = '';
+  isRenderable(path) {
+    return this.renderer.isRenderable(path);
+  }
 
-  return new Promise((resolve, reject) => {
-    if (!data) return reject(new TypeError('No input file or string!'));
-    if (data.text != null) return resolve(data.text);
-    if (!data.path) return reject(new TypeError('No input file or string!'));
+  isRenderableSync(path) {
+    return this.renderer.isRenderableSync(path);
+  }
 
-    fs.readFile(data.path).then(resolve, reject);
-  }).then(text => {
-    data.text = text;
-    ext = data.engine || getExtname(data.path);
-    if (!ext || !this.isRenderable(ext)) return text;
+  getOutput(path) {
+    return this.renderer.getOutput(path);
+  }
 
-    const renderer = this.getRenderer(ext);
-    return Reflect.apply(renderer, ctx, [data, options]);
-  }).then(result => {
-    result = toString(result, data);
-    if (data.onRenderEnd) {
-      return data.onRenderEnd(result);
-    }
+  getRenderer(ext, sync) {
+    return this.renderer.get(ext, sync);
+  }
 
-    return result;
-  }).then(result => {
-    const output = this.getOutput(ext) || ext;
-    return ctx.execFilter(`after_render:${output}`, result, {
-      context: ctx,
-      args: [data]
-    });
-  }).asCallback(callback);
-};
+  getRendererSync(ext) {
+    return this.getRenderer(ext, true);
+  }
 
-Render.prototype.renderSync = function(data, options) {
-  if (!data) throw new TypeError('No input file or string!');
+  render(data, options, callback) {
+    if (!callback && typeof options === 'function') {
+      callback = options;
+      options = {};
+    }
 
-  options = options || {};
+    const ctx = this.context;
+    let ext = '';
+
+    return new Promise((resolve, reject) => {
+      if (!data) return reject(new TypeError('No input file or string!'));
+      if (data.text != null) return resolve(data.text);
+      if (!data.path) return reject(new TypeError('No input file or string!'));
+
+      readFile(data.path).then(resolve, reject);
+    }).then(text => {
+      data.text = text;
+      ext = data.engine || getExtname(data.path);
+      if (!ext || !this.isRenderable(ext)) return text;
+
+      const renderer = this.getRenderer(ext);
+      return Reflect.apply(renderer, ctx, [data, options]);
+    }).then(result => {
+      result = toString(result, data);
+      if (data.onRenderEnd) {
+        return data.onRenderEnd(result);
+      }
+
+      return result;
+    }).then(result => {
+      const output = this.getOutput(ext) || ext;
+      return ctx.execFilter(`after_render:${output}`, result, {
+        context: ctx,
+        args: [data]
+      });
+    }).asCallback(callback);
+  }
 
-  const ctx = this.context;
+  renderSync(data, options) {
+    if (!data) throw new TypeError('No input file or string!');
 
-  if (data.text == null) {
-    if (!data.path) throw new TypeError('No input file or string!');
-    data.text = fs.readFileSync(data.path);
-  }
+    options = options || {};
 
-  if (data.text == null) throw new TypeError('No input file or string!');
+    const ctx = this.context;
 
-  const ext = data.engine || getExtname(data.path);
-  let result;
+    if (data.text == null) {
+      if (!data.path) throw new TypeError('No input file or string!');
+      data.text = readFileSync(data.path);
+    }
 
-  if (ext && this.isRenderableSync(ext)) {
-    const renderer = this.getRendererSync(ext);
-    result = Reflect.apply(renderer, ctx, [data, options]);
-  } else {
-    result = data.text;
-  }
+    if (data.text == null) throw new TypeError('No input file or string!');
 
-  const output = this.getOutput(ext) || ext;
-  result = toString(result, data);
+    const ext = data.engine || getExtname(data.path);
+    let result;
 
-  if (data.onRenderEnd) {
-    result = data.onRenderEnd(result);
-  }
+    if (ext && this.isRenderableSync(ext)) {
+      const renderer = this.getRendererSync(ext);
+      result = Reflect.apply(renderer, ctx, [data, options]);
+    } else {
+      result = data.text;
+    }
 
-  return ctx.execFilterSync(`after_render:${output}`, result, {
-    context: ctx,
-    args: [data]
-  });
-};
+    const output = this.getOutput(ext) || ext;
+    result = toString(result, data);
 
-function toString(result, options) {
-  if (!Object.prototype.hasOwnProperty.call(options, 'toString') || typeof result === 'string') return result;
+    if (data.onRenderEnd) {
+      result = data.onRenderEnd(result);
+    }
 
-  if (typeof options.toString === 'function') {
-    return options.toString(result);
-  } else if (typeof result === 'object') {
-    return JSON.stringify(result);
-  } else if (result.toString) {
-    return result.toString();
+    return ctx.execFilterSync(`after_render:${output}`, result, {
+      context: ctx,
+      args: [data]
+    });
   }
-
-  return result;
 }
 
 module.exports = Render;