refactor: replace Object.assign with util._extend

lib/theme/view.js

@@ -2,9 +2,20 @@
 
 const { dirname, extname, join } = require('path');
 const yfm = require('hexo-front-matter');
-const omit = require('lodash/omit');
 const Promise = require('bluebird');
 
+/* Although this API is already deprecated in Node.js 6, but util._extend() is still about
+ * 3x faster than Object.assign(). Enen Node.js itself is still using util._extend()
+ *
+ * https://github.com/nodejs/node/pull/4903
+ * https://github.com/nodejs/node/pull/4593
+ * https://github.com/nodejs/node/pull/6977
+ * https://github.com/nodejs/node/pull/7208
+ * https://github.com/nodejs/node/pull/7255
+ */
+// eslint-disable-next-line node/no-deprecated-api
+const { _extend } = require('util');
+
 function View(path, data) {
   this.path = path;
   this.source = join(this._theme.base, 'layout', path);
@@ -31,7 +42,7 @@ View.prototype.render = function(options, callback) {
     const layoutView = this._resolveLayout(layout);
     if (!layoutView) return result;
 
-    const layoutLocals = Object.assign({}, locals, {
+    const layoutLocals = _extend({}, locals, {
       body: result,
       layout: false
     });
@@ -51,7 +62,7 @@ View.prototype.renderSync = function(options = {}) {
   const layoutView = this._resolveLayout(layout);
   if (!layoutView) return result;
 
-  const layoutLocals = Object.assign({}, locals, {
+  const layoutLocals = _extend({}, locals, {
     body: result,
     layout: false
   });
@@ -60,8 +71,9 @@ View.prototype.renderSync = function(options = {}) {
 };
 
 View.prototype._buildLocals = function(locals) {
-
-  return Object.assign({}, locals, Object.getPrototypeOf(locals), omit(this.data, ['layout', '_content']), {
+  // eslint-disable-next-line no-unused-vars
+  const { layout, _content, ...data } = this.data;
+  return _extend({}, locals, Object.getPrototypeOf(locals), data, {
     filename: this.source
   });
 };