diff --git a/lib/box/index.js b/lib/box/index.js
index 03a2ffd952..7519200df9 100644
--- a/lib/box/index.js
+++ b/lib/box/index.js
@@ -106,12 +106,8 @@ Box.prototype._readDir = function(base, fn, prefix = '') {
   const self = this;
   const { ignore } = self;
 
-  if (base && ignore && ignore.length) {
-    for (let i = 0, len = ignore.length; i < len; i++) {
-      if (minimatch(base, ignore[i])) {
-        return Promise.resolve('Ignoring dir.');
-      }
-    }
+  if (base && ignore && ignore.length && ignore.some(item => minimatch(base, item))) {
+    return Promise.resolve('Ignoring dir.');
   }
 
   return fs.readdir(base).map(path => fs.stat(join(base, path)).then(stats => {
diff --git a/lib/extend/filter.js b/lib/extend/filter.js
index b8ddc42889..e7b50522df 100644
--- a/lib/extend/filter.js
+++ b/lib/extend/filter.js
@@ -45,12 +45,9 @@ Filter.prototype.unregister = function(type, fn) {
   const list = this.list(type);
   if (!list || !list.length) return;
 
-  for (let i = 0, len = list.length; i < len; i++) {
-    if (list[i] === fn) {
-      list.splice(i, 1);
-      break;
-    }
-  }
+  const index = list.findIndex(item => item === fn);
+
+  if (index != null) list.splice(index, 1);
 };
 
 Filter.prototype.exec = function(type, data, options = {}) {
diff --git a/lib/extend/tag.js b/lib/extend/tag.js
index 12e8c06549..1ce52022de 100644
--- a/lib/extend/tag.js
+++ b/lib/extend/tag.js
@@ -33,12 +33,10 @@ Tag.prototype.register = function(name, fn, options) {
     } else {
       tag = new NunjucksAsyncTag(name, fn);
     }
+  } else if (options.ends) {
+    tag = new NunjucksBlock(name, fn);
   } else {
-    if (options.ends) {
-      tag = new NunjucksBlock(name, fn);
-    } else {
-      tag = new NunjucksTag(name, fn);
-    }
+    tag = new NunjucksTag(name, fn);
   }
 
   this.env.addExtension(name, tag);
@@ -77,11 +75,11 @@ NunjucksTag.prototype.parse = function(parser, nodes, lexer) {
 NunjucksTag.prototype._parseArgs = (parser, nodes, lexer) => {
   const tag = parser.nextToken();
   const node = new nodes.NodeList(tag.lineno, tag.colno);
-  let token;
-
   const argarray = new nodes.Array(tag.lineno, tag.colno);
 
+  let token;
   let argitem = '';
+
   while ((token = parser.nextToken(true))) {
     if (token.type === lexer.TOKEN_WHITESPACE || token.type === lexer.TOKEN_BLOCK_END) {
       if (argitem !== '') {
diff --git a/lib/hexo/index.js b/lib/hexo/index.js
index bab96173eb..20ccae0cfe 100644
--- a/lib/hexo/index.js
+++ b/lib/hexo/index.js
@@ -350,19 +350,14 @@ Hexo.prototype._generate = function(options = {}) {
 
       const path = route.format(item.path);
       const { data } = item;
-      let { layout } = item;
 
       newRouteList.push(path);
 
-      if (!layout) {
+      if (!item.layout) {
         return route.set(path, data);
       }
 
-      if (Array.isArray(layout)) {
-        layout = layout.filter((item, index, self) => self.indexOf(item) === index);
-      } else {
-        layout = [layout];
-      }
+      const layout = Array.isArray(item.layout) ? item.layout.filter((item, index, self) => self.indexOf(item) === index) : [item.layout];
 
       const locals = new Locals(path, data);
       const layoutLength = layout.length;
@@ -378,11 +373,9 @@ Hexo.prototype._generate = function(options = {}) {
           route.set(path, () => {
             if (options.cache && cache != null) return cache;
 
-            let view, name;
-
             for (let i = 0; i < layoutLength; i++) {
-              name = layout[i];
-              view = theme.getView(name);
+              const name = layout[i];
+              const view = theme.getView(name);
 
               if (view) {
                 log.debug('Rendering %s: %s', name, chalk.magenta(path));
diff --git a/lib/hexo/load_config.js b/lib/hexo/load_config.js
index 629733b78a..6d9d3f890b 100644
--- a/lib/hexo/load_config.js
+++ b/lib/hexo/load_config.js
@@ -49,14 +49,7 @@ function findConfigPath(path) {
   const { dir, name } = parse(path);
 
   return fs.readdir(dir).then(files => {
-    let item;
-
-    for (let i = 0, len = files.length; i < len; i++) {
-      item = files[i];
-
-      if (item.startsWith(name)) {
-        return join(dir, item);
-      }
-    }
+    const item = files.find(item => item.startsWith(name));
+    if (item != null) return join(dir, item);
   });
 }
diff --git a/lib/hexo/locals.js b/lib/hexo/locals.js
index 6c127d69fe..0ae994dc45 100644
--- a/lib/hexo/locals.js
+++ b/lib/hexo/locals.js
@@ -24,13 +24,7 @@ Locals.prototype.set = function(name, value) {
   if (typeof name !== 'string') throw new TypeError('name must be a string!');
   if (value == null) throw new TypeError('value is required!');
 
-  let getter;
-
-  if (typeof value === 'function') {
-    getter = value;
-  } else {
-    getter = () => value;
-  }
+  const getter = typeof value === 'function' ? value : () => value;
 
   this.getters[name] = getter;
   this.cache[name] = null;
@@ -56,12 +50,10 @@ Locals.prototype.invalidate = function() {
 Locals.prototype.toObject = function() {
   const result = {};
   const keys = Object.keys(this.getters);
-  let key = '';
-  let item;
 
   for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
-    item = this.get(key);
+    const key = keys[i];
+    const item = this.get(key);
 
     if (item != null) result[key] = item;
   }
diff --git a/lib/hexo/multi_config_path.js b/lib/hexo/multi_config_path.js
index 65bf1205c1..afc3b40b00 100644
--- a/lib/hexo/multi_config_path.js
+++ b/lib/hexo/multi_config_path.js
@@ -7,15 +7,14 @@ const yml = require('js-yaml');
 
 module.exports = ctx => function multiConfigPath(base, configPaths, outputDir) {
   const { log } = ctx;
-
   const defaultPath = join(base, '_config.yml');
-  let paths;
 
   if (!configPaths) {
     log.w('No config file entered.');
     return join(base, '_config.yml');
   }
 
+  let paths;
   // determine if comma or space separated
   if (configPaths.includes(',')) {
     paths = configPaths.replace(' ', '').split(',');
@@ -37,13 +36,7 @@ module.exports = ctx => function multiConfigPath(base, configPaths, outputDir) {
   const combinedConfig = {};
   let count = 0;
   for (let i = 0; i < numPaths; i++) {
-    let configPath = '';
-
-    if (isAbsolute(paths[i])) {
-      configPath = paths[i];
-    } else {
-      configPath = join(base, paths[i]);
-    }
+    const configPath = isAbsolute(paths[i]) ? paths[i] : join(base, paths[i]);
 
     if (!fs.existsSync(configPath)) {
       log.w(`Config file ${paths[i]} not found.`);
diff --git a/lib/hexo/post.js b/lib/hexo/post.js
index 6549be0435..2db4c43a4e 100644
--- a/lib/hexo/post.js
+++ b/lib/hexo/post.js
@@ -119,14 +119,9 @@ Post.prototype._renderScaffold = function(data) {
   }).then(frontMatter => {
     const { separator } = yfmSplit;
     const jsonMode = separator[0] === ';';
-    let obj;
 
     // Parse front-matter
-    if (jsonMode) {
-      obj = JSON.parse(`{${frontMatter}}`);
-    } else {
-      obj = yaml.load(frontMatter);
-    }
+    const obj = jsonMode ? JSON.parse(`{${frontMatter}}`) : yaml.load(frontMatter);
 
     // Add data which are not in the front-matter
     for (const key of Object.keys(data)) {
diff --git a/lib/hexo/register_models.js b/lib/hexo/register_models.js
index 54073da006..6245e122a1 100644
--- a/lib/hexo/register_models.js
+++ b/lib/hexo/register_models.js
@@ -6,10 +6,9 @@ module.exports = ctx => {
   const db = ctx.database;
 
   const keys = Object.keys(models);
-  let key = '';
 
   for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
+    const key = keys[i];
     db.model(key, models[key](ctx));
   }
 };
diff --git a/lib/hexo/router.js b/lib/hexo/router.js
index 091eeceba2..8339bf2d94 100644
--- a/lib/hexo/router.js
+++ b/lib/hexo/router.js
@@ -33,16 +33,7 @@ Router.format = Router.prototype.format = path => {
 
 Router.prototype.list = function() {
   const { routes } = this;
-  const keys = Object.keys(routes);
-  const arr = [];
-  let key;
-
-  for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
-    if (routes[key]) arr.push(key);
-  }
-
-  return arr;
+  return Object.keys(routes).filter(key => routes[key]);
 };
 
 Router.prototype.get = function(path) {
diff --git a/lib/hexo/scaffold.js b/lib/hexo/scaffold.js
index b7c37ff241..0d1428470e 100644
--- a/lib/hexo/scaffold.js
+++ b/lib/hexo/scaffold.js
@@ -35,14 +35,7 @@ Scaffold.prototype._listDir = function() {
 };
 
 Scaffold.prototype._getScaffold = function(name) {
-  return this._listDir().then(list => {
-    let item;
-
-    for (let i = 0, len = list.length; i < len; i++) {
-      item = list[i];
-      if (item.name === name) return item;
-    }
-  });
+  return this._listDir().then(list => list.find(item => item.name === name));
 };
 
 Scaffold.prototype.get = function(name, callback) {
diff --git a/lib/models/cache.js b/lib/models/cache.js
index e855f32a58..f4cef7d94d 100644
--- a/lib/models/cache.js
+++ b/lib/models/cache.js
@@ -13,7 +13,6 @@ module.exports = ctx => {
   Cache.static('compareFile', function(id, hashFn, statFn) {
     const cache = this.findById(id);
     const self = this;
-    let mtime;
 
     // If cache does not exist, then it must be a new file. We have to get both
     // file hash and stats.
@@ -27,6 +26,8 @@ module.exports = ctx => {
       });
     }
 
+    let mtime;
+
     // Get file stats
     return statFn(id).then(stats => {
       mtime = stats.mtime;
diff --git a/lib/models/category.js b/lib/models/category.js
index 0de0e5800d..a025b5316a 100644
--- a/lib/models/category.js
+++ b/lib/models/category.js
@@ -10,17 +10,19 @@ module.exports = ctx => {
   });
 
   Category.virtual('slug').get(function() {
-    const map = ctx.config.category_map || {};
     let name = this.name;
-    let str = '';
 
     if (!name) return;
 
+    let str = '';
+
     if (this.parent) {
       const parent = ctx.model('Category').findById(this.parent);
       str += `${parent.slug}/`;
     }
 
+    const map = ctx.config.category_map || {};
+
     name = map[name] || name;
     str += slugize(name, {transform: ctx.config.filename_case});
 
diff --git a/lib/plugins/console/config.js b/lib/plugins/console/config.js
index 3561f14676..e0183b9c3b 100644
--- a/lib/plugins/console/config.js
+++ b/lib/plugins/console/config.js
@@ -30,15 +30,9 @@ function configConsole(args) {
   }).then(config => {
     if (!config) config = {};
 
-    let result = '';
-
     setProperty(config, key, castValue(value));
 
-    if (ext === '.json') {
-      result = JSON.stringify(config);
-    } else {
-      result = yaml.dump(config);
-    }
+    const result = ext === '.json' ? JSON.stringify(config) : yaml.dump(config);
 
     return fs.writeFile(configPath, result);
   });
@@ -58,11 +52,10 @@ function getProperty(obj, key) {
 function setProperty(obj, key, value) {
   const split = key.split('.');
   let cursor = obj;
-  let name = '';
   const lastKey = split.pop();
 
   for (let i = 0, len = split.length; i < len; i++) {
-    name = split[i];
+    const name = split[i];
     cursor = cursor[name] = cursor[name] || {};
   }
 
diff --git a/lib/plugins/console/list/route.js b/lib/plugins/console/list/route.js
index 912e008233..389dd59457 100644
--- a/lib/plugins/console/list/route.js
+++ b/lib/plugins/console/list/route.js
@@ -17,14 +17,14 @@ function listRoute() {
 
 function buildTree(routes) {
   const obj = {};
-  let item, j, lenj, seg, cursor;
+  let cursor;
 
   for (let i = 0, len = routes.length; i < len; i++) {
-    item = routes[i].split('/');
+    const item = routes[i].split('/');
     cursor = obj;
 
-    for (j = 0, lenj = item.length; j < lenj; j++) {
-      seg = item[j];
+    for (let j = 0, lenj = item.length; j < lenj; j++) {
+      const seg = item[j];
       cursor = cursor[seg] = cursor[seg] || {};
     }
   }
@@ -35,11 +35,10 @@ function buildTree(routes) {
 function buildNodes(tree) {
   const keys = Object.keys(tree);
   const nodes = [];
-  let key, item;
 
   for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
-    item = tree[key];
+    const key = keys[i];
+    const item = tree[key];
 
     if (Object.keys(item).length) {
       nodes.push({
diff --git a/lib/plugins/console/new.js b/lib/plugins/console/new.js
index daa6871267..bc33082fe3 100644
--- a/lib/plugins/console/new.js
+++ b/lib/plugins/console/new.js
@@ -31,11 +31,10 @@ function newConsole(args) {
   };
 
   const keys = Object.keys(args);
-  let key = '';
   const self = this;
 
   for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
+    const key = keys[i];
     if (!reservedKeys[key]) data[key] = args[key];
   }
 
diff --git a/lib/plugins/filter/before_post_render/backtick_code_block.js b/lib/plugins/filter/before_post_render/backtick_code_block.js
index 68b20dd7d5..06dec6739a 100644
--- a/lib/plugins/filter/before_post_render/backtick_code_block.js
+++ b/lib/plugins/filter/before_post_render/backtick_code_block.js
@@ -34,13 +34,8 @@ function backtickCodeBlock(data) {
     }
 
     if (args) {
-      let match;
+      const match = rAllOptions.exec(args) || rLangCaption.exec(args);
 
-      if (rAllOptions.test(args)) {
-        match = args.match(rAllOptions);
-      } else if (rLangCaption.test(args)) {
-        match = args.match(rLangCaption);
-      }
 
       if (match) {
         options.lang = match[1];
diff --git a/lib/plugins/filter/new_post_path.js b/lib/plugins/filter/new_post_path.js
index a0fe544e9f..4773c0cca1 100644
--- a/lib/plugins/filter/new_post_path.js
+++ b/lib/plugins/filter/new_post_path.js
@@ -25,12 +25,13 @@ function newPostPathFilter(data = {}, replace) {
   const newPostName = config.new_post_name;
   const permalinkDefaults = config.permalink_defaults;
   const { path, layout, slug } = data;
-  let target = '';
 
   if (!permalink || permalink.rule !== newPostName) {
     permalink = new Permalink(newPostName);
   }
 
+  let target = '';
+
   if (path) {
     switch (layout) {
       case 'page':
@@ -57,7 +58,6 @@ function newPostPathFilter(data = {}, replace) {
       default: {
         const date = moment(data.date || Date.now());
         const keys = Object.keys(data);
-        let key = '';
 
         const filenameData = {
           year: date.format('YYYY'),
@@ -69,7 +69,7 @@ function newPostPathFilter(data = {}, replace) {
         };
 
         for (let i = 0, len = keys.length; i < len; i++) {
-          key = keys[i];
+          const key = keys[i];
           if (!reservedKeys[key]) filenameData[key] = data[key];
         }
 
diff --git a/lib/plugins/filter/post_permalink.js b/lib/plugins/filter/post_permalink.js
index 39980897ae..7a958f9a3c 100644
--- a/lib/plugins/filter/post_permalink.js
+++ b/lib/plugins/filter/post_permalink.js
@@ -32,10 +32,9 @@ function postPermalinkFilter(data) {
   }
 
   const keys = Object.keys(data);
-  let key = '';
 
   for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
+    const key = keys[i];
     if (meta.hasOwnProperty(key)) continue;
 
     // Use Object.getOwnPropertyDescriptor to copy getters to avoid "Maximum call
diff --git a/lib/plugins/generator/asset.js b/lib/plugins/generator/asset.js
index 1ff14359be..48cf3054fa 100644
--- a/lib/plugins/generator/asset.js
+++ b/lib/plugins/generator/asset.js
@@ -9,9 +9,8 @@ function assetGenerator(locals) {
   const self = this;
 
   function process(name) {
-    return Promise.filter(self.model(name).toArray(), asset => fs.exists(asset.source).then(exist => {
-      if (exist) return exist;
-      return asset.remove().thenReturn(exist);
+    return Promise.filter(self.model(name).toArray(), asset => fs.exists(asset.source).tap(exist => {
+      if (!exist) return asset.remove();
     })).map(asset => {
       const { source } = asset;
       let { path } = asset;
diff --git a/lib/plugins/helper/css.js b/lib/plugins/helper/css.js
index 9383c4ed3f..0fcd0ab26c 100644
--- a/lib/plugins/helper/css.js
+++ b/lib/plugins/helper/css.js
@@ -1,22 +1,18 @@
 'use strict';
 
 function cssHelper(...args) {
-  let result = '';
-
-  for (let i = 0, len = args.length; i < len; i++) {
-    let path = args[i];
-
-    if (i) result += '\n';
+  return args.reduce((_result, path, i) => {
+    if (i) _result += '\n';
 
     if (Array.isArray(path)) {
-      result += Reflect.apply(cssHelper, this, path);
+      _result += Reflect.apply(cssHelper, this, path);
+
     } else {
       if (!path.includes('?') && !path.endsWith('.css')) path += '.css';
-      result += `<link rel="stylesheet" href="${this.url_for(path)}">`;
+      _result += `<link rel="stylesheet" href="${this.url_for(path)}">`;
     }
-  }
-
-  return result;
+    return _result;
+  }, '');
 }
 
 module.exports = cssHelper;
diff --git a/lib/plugins/helper/image_tag.js b/lib/plugins/helper/image_tag.js
index b5b9bebb84..8fc8d92da9 100644
--- a/lib/plugins/helper/image_tag.js
+++ b/lib/plugins/helper/image_tag.js
@@ -3,17 +3,9 @@
 const { htmlTag } = require('hexo-util');
 
 function imageTagHelper(path, options = {}) {
-  const attrs = {
+  const attrs = Object.assign({
     src: this.url_for(path)
-  };
-
-  const keys = Object.keys(options);
-  let key = '';
-
-  for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
-    attrs[key] = options[key];
-  }
+  }, options);
 
   if (attrs.class && Array.isArray(attrs.class)) {
     attrs.class = attrs.class.join(' ');
diff --git a/lib/plugins/helper/link_to.js b/lib/plugins/helper/link_to.js
index c0c52c1c61..ed9605c9f6 100644
--- a/lib/plugins/helper/link_to.js
+++ b/lib/plugins/helper/link_to.js
@@ -7,18 +7,10 @@ function linkToHelper(path, text, options = {}) {
 
   if (!text) text = path.replace(/^https?:\/\/|\/$/g, '');
 
-  const attrs = {
+  const attrs = Object.assign({
     href: this.url_for(path),
     title: text
-  };
-
-  const keys = Object.keys(options);
-  let key = '';
-
-  for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
-    attrs[key] = options[key];
-  }
+  }, options);
 
   if (attrs.external) {
     attrs.target = '_blank';
diff --git a/lib/plugins/helper/list_archives.js b/lib/plugins/helper/list_archives.js
index 0be4a18282..5923ec871a 100644
--- a/lib/plugins/helper/list_archives.js
+++ b/lib/plugins/helper/list_archives.js
@@ -59,13 +59,11 @@ function listArchivesHelper(options = {}) {
     return self.url_for(url);
   }
 
-  let item, i, len;
-
   if (style === 'list') {
     result += `<ul class="${className}-list">`;
 
-    for (i = 0, len = data.length; i < len; i++) {
-      item = data[i];
+    for (let i = 0, len = data.length; i < len; i++) {
+      const item = data[i];
 
       result += `<li class="${className}-list-item">`;
 
@@ -82,8 +80,8 @@ function listArchivesHelper(options = {}) {
 
     result += '</ul>';
   } else {
-    for (i = 0, len = data.length; i < len; i++) {
-      item = data[i];
+    for (let i = 0, len = data.length; i < len; i++) {
+      const item = data[i];
 
       if (i) result += separator;
 
diff --git a/lib/plugins/helper/list_categories.js b/lib/plugins/helper/list_categories.js
index 458ee03787..ecf1114406 100644
--- a/lib/plugins/helper/list_categories.js
+++ b/lib/plugins/helper/list_categories.js
@@ -17,7 +17,6 @@ function listCategoriesHelper(categories, options) {
   const order = options.order || 1;
   const showCurrent = options.show_current || false;
   const childrenIndicator = options.hasOwnProperty('children_indicator') ? options.children_indicator : false;
-  let result = '';
   const self = this;
 
   function prepareQuery(parent) {
@@ -52,17 +51,10 @@ function listCategoriesHelper(categories, options) {
         }
 
         // special case: category page
-        if (!isCurrent && self.page.base) {
-          if (self.page.base.startsWith(cat.path)) {
-            isCurrent = true;
-          }
-        }
+        isCurrent = isCurrent || (self.page.base && self.page.base.startsWith(cat.path));
       }
 
-      let additionalClassName = '';
-      if (child && childrenIndicator) {
-        additionalClassName = ` ${childrenIndicator}`;
-      }
+      const additionalClassName = child && childrenIndicator ? ` ${childrenIndicator}` : '';
 
       result += `<li class="${className}-list-item${additionalClassName}">`;
 
@@ -108,12 +100,10 @@ function listCategoriesHelper(categories, options) {
   }
 
   if (style === 'list') {
-    result += `<ul class="${className}-list">${hierarchicalList(0)}</ul>`;
-  } else {
-    result += flatList(0);
+    return `<ul class="${className}-list">${hierarchicalList(0)}</ul>`;
   }
 
-  return result;
+  return flatList(0);
 }
 
 module.exports = listCategoriesHelper;
diff --git a/lib/plugins/helper/list_posts.js b/lib/plugins/helper/list_posts.js
index b461ab9987..20cc21d48d 100644
--- a/lib/plugins/helper/list_posts.js
+++ b/lib/plugins/helper/list_posts.js
@@ -13,7 +13,6 @@ function listPostsHelper(posts, options) {
   const order = options.order || -1;
   const className = options.class || 'post';
   const amount = options.amount || 6;
-  let result = '';
   const self = this;
 
   // Sort the posts
@@ -22,6 +21,8 @@ function listPostsHelper(posts, options) {
   // Limit the number of posts
   if (amount) posts = posts.limit(amount);
 
+  let result = '';
+
   if (style === 'list') {
     result += `<ul class="${className}-list">`;
 
diff --git a/lib/plugins/helper/mail_to.js b/lib/plugins/helper/mail_to.js
index da5faf2493..5443388106 100644
--- a/lib/plugins/helper/mail_to.js
+++ b/lib/plugins/helper/mail_to.js
@@ -7,18 +7,10 @@ function mailToHelper(path, text, options = {}) {
   if (Array.isArray(path)) path = path.join(',');
   if (!text) text = path;
 
-  const attrs = {
+  const attrs = Object.assign({
     href: `mailto:${path}`,
     title: text
-  };
-
-  const keys = Object.keys(options);
-  let key = '';
-
-  for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
-    attrs[key] = options[key];
-  }
+  }, options);
 
   if (attrs.class && Array.isArray(attrs.class)) {
     attrs.class = attrs.class.join(' ');
diff --git a/lib/plugins/helper/number_format.js b/lib/plugins/helper/number_format.js
index 6fc37f62e0..0db807eb76 100644
--- a/lib/plugins/helper/number_format.js
+++ b/lib/plugins/helper/number_format.js
@@ -7,7 +7,6 @@ function numberFormatHelper(num, options = {}) {
   const delimiter = options.delimiter || ',';
   const separator = options.separator || '.';
   const { precision } = options;
-  let i, len;
 
   if (delimiter) {
     const beforeArr = [];
@@ -16,7 +15,7 @@ function numberFormatHelper(num, options = {}) {
 
     if (beforeFirst) beforeArr.push(before.substr(0, beforeFirst));
 
-    for (i = beforeFirst; i < beforeLength; i += 3) {
+    for (let i = beforeFirst; i < beforeLength; i += 3) {
       beforeArr.push(before.substr(i, 3));
     }
 
@@ -34,7 +33,7 @@ function numberFormatHelper(num, options = {}) {
       afterResult = after.substr(0, precision - 1) + (afterLast < 5 ? last : last + 1);
     } else {
       afterResult = after;
-      for (i = 0, len = precision - afterLength; i < len; i++) {
+      for (let i = 0, len = precision - afterLength; i < len; i++) {
         afterResult += '0';
       }
     }
diff --git a/lib/plugins/helper/open_graph.js b/lib/plugins/helper/open_graph.js
index 9e892a17e9..58341d22ef 100644
--- a/lib/plugins/helper/open_graph.js
+++ b/lib/plugins/helper/open_graph.js
@@ -42,7 +42,6 @@ function openGraphHelper(options = {}) {
   const twitterCard = options.twitter_card || 'summary';
   const updated = options.updated !== false ? options.updated || page.updated : false;
   const language = options.language || page.lang || page.language || config.language;
-  let result = '';
 
   if (!Array.isArray(images)) images = [images];
 
@@ -68,6 +67,8 @@ function openGraphHelper(options = {}) {
     });
   }
 
+  let result = '';
+
   if (description) {
     result += meta('description', description, false);
   }
diff --git a/lib/plugins/helper/paginator.js b/lib/plugins/helper/paginator.js
index 018edc36a9..69fef89028 100644
--- a/lib/plugins/helper/paginator.js
+++ b/lib/plugins/helper/paginator.js
@@ -11,8 +11,6 @@ function paginatorHelper(options = {}) {
   const prevText = options.prev_text || 'Prev';
   const nextText = options.next_text || 'Next';
   const prevNext = options.hasOwnProperty('prev_next') ? options.prev_next : true;
-  let result = '';
-  let i;
 
   if (!current) return '';
 
@@ -26,6 +24,7 @@ function paginatorHelper(options = {}) {
     return `<a class="page-number" href="${link(i)}">${transform ? transform(i) : i}</a>`;
   }
 
+  let result = '';
   // Display the link to the previous page
   if (prevNext && current > 1) {
     result += `<a class="extend prev" rel="prev" href="${link(current - 1)}">${prevText}</a>`;
@@ -33,7 +32,7 @@ function paginatorHelper(options = {}) {
 
   if (options.show_all) {
     // Display pages on the left side of the current page
-    for (i = 1; i < current; i++) {
+    for (let i = 1; i < current; i++) {
       result += pageLink(i);
     }
 
@@ -41,7 +40,7 @@ function paginatorHelper(options = {}) {
     result += currentPage;
 
     // Display pages on the right side of the current page
-    for (i = current + 1; i <= total; i++) {
+    for (let i = current + 1; i <= total; i++) {
       result += pageLink(i);
     }
   } else {
@@ -53,7 +52,7 @@ function paginatorHelper(options = {}) {
     const spaceHtml = `<span class="space">${space}</span>`;
 
     // Display pages on the left edge
-    for (i = 1; i <= leftEnd; i++) {
+    for (let i = 1; i <= leftEnd; i++) {
       result += pageLink(i);
     }
 
@@ -64,7 +63,7 @@ function paginatorHelper(options = {}) {
 
     // Display left middle pages
     if (leftMid > leftEnd) {
-      for (i = leftMid; i < current; i++) {
+      for (let i = leftMid; i < current; i++) {
         result += pageLink(i);
       }
     }
@@ -74,7 +73,7 @@ function paginatorHelper(options = {}) {
 
     // Display right middle pages
     if (rightMid < rightEnd) {
-      for (i = current + 1; i <= rightMid; i++) {
+      for (let i = current + 1; i <= rightMid; i++) {
         result += pageLink(i);
       }
     }
@@ -85,7 +84,7 @@ function paginatorHelper(options = {}) {
     }
 
     // Dispaly pages on the right edge
-    for (i = rightEnd; i <= total; i++) {
+    for (let i = rightEnd; i <= total; i++) {
       result += pageLink(i);
     }
   }
diff --git a/lib/plugins/helper/tagcloud.js b/lib/plugins/helper/tagcloud.js
index d49625ca62..6398f9a4f1 100644
--- a/lib/plugins/helper/tagcloud.js
+++ b/lib/plugins/helper/tagcloud.js
@@ -263,33 +263,31 @@ Color.prototype.parse = function(color) {
     return;
   }
 
-  let match, txt, code;
-
   if (rHex3.test(color)) {
-    txt = color.substring(1);
-    code = parseInt(txt, 16);
+    const txt = color.substring(1);
+    const code = parseInt(txt, 16);
 
     this.r = ((code & 0xF00) >> 8) * 17;
     this.g = ((code & 0xF0) >> 4) * 17;
     this.b = (code & 0xF) * 17;
     this.a = 1;
   } else if (rHex6.test(color)) {
-    txt = color.substring(1);
-    code = parseInt(txt, 16);
+    const txt = color.substring(1);
+    const code = parseInt(txt, 16);
 
     this.r = (code & 0xFF0000) >> 16;
     this.g = (code & 0xFF00) >> 8;
     this.b = code & 0xFF;
     this.a = 1;
   } else if (rRGB.test(color)) {
-    match = color.match(rRGB);
+    const match = color.match(rRGB);
 
     this.r = match[1] | 0;
     this.g = match[2] | 0;
     this.b = match[3] | 0;
     this.a = match[4] ? +match[4] : 1;
   } else if (rHSL.test(color)) {
-    match = color.match(rHSL);
+    const match = color.match(rHSL);
 
     const h = +match[1] / 360;
     const s = +match[2] / 100;
diff --git a/lib/plugins/helper/toc.js b/lib/plugins/helper/toc.js
index ea74ae011b..04cc47ff3a 100644
--- a/lib/plugins/helper/toc.js
+++ b/lib/plugins/helper/toc.js
@@ -19,7 +19,6 @@ function tocHelper(str, options = {}) {
   const lastNumber = [0, 0, 0, 0, 0, 0];
   let firstLevel = 0;
   let lastLevel = 0;
-  let i = 0;
 
   headings.each(function() {
     const level = +this.name[1];
@@ -28,12 +27,12 @@ function tocHelper(str, options = {}) {
 
     lastNumber[level - 1]++;
 
-    for (i = level; i <= 5; i++) {
+    for (let i = level; i <= 5; i++) {
       lastNumber[i] = 0;
     }
 
     if (firstLevel) {
-      for (i = level; i < lastLevel; i++) {
+      for (let i = level; i < lastLevel; i++) {
         result += '</li></ol>';
       }
 
@@ -52,7 +51,7 @@ function tocHelper(str, options = {}) {
     if (listNumber) {
       result += `<span class="${className}-number">`;
 
-      for (i = firstLevel - 1; i < level; i++) {
+      for (let i = firstLevel - 1; i < level; i++) {
         result += `${lastNumber[i]}.`;
       }
 
@@ -64,7 +63,7 @@ function tocHelper(str, options = {}) {
     lastLevel = level;
   });
 
-  for (i = firstLevel - 1; i < lastLevel; i++) {
+  for (let i = firstLevel - 1; i < lastLevel; i++) {
     result += '</li></ol>';
   }
 
diff --git a/lib/plugins/processor/common.js b/lib/plugins/processor/common.js
index ccd5a3aa1e..6a7f8f5c4c 100644
--- a/lib/plugins/processor/common.js
+++ b/lib/plugins/processor/common.js
@@ -50,12 +50,5 @@ exports.isMatch = (path, patterns) => {
   if (!patterns) return false;
   if (!Array.isArray(patterns)) patterns = [patterns];
 
-  patterns = patterns.filter(value => value);
-  if (!patterns.length) return false;
-
-  for (let i = 0, len = patterns.length; i < len; i++) {
-    if (minimatch(path, patterns[i])) return true;
-  }
-
-  return false;
+  return patterns.some(pattern => pattern && minimatch(path, pattern));
 };
diff --git a/lib/plugins/processor/post.js b/lib/plugins/processor/post.js
index 3e8ea2e50b..cf422d9099 100644
--- a/lib/plugins/processor/post.js
+++ b/lib/plugins/processor/post.js
@@ -48,7 +48,6 @@ module.exports = ctx => {
       const data = yfm(content);
       const info = parseFilename(config.new_post_name, path);
       const keys = Object.keys(info);
-      let key;
 
       data.source = file.path;
       data.raw = content;
@@ -61,7 +60,7 @@ module.exports = ctx => {
       }
 
       for (let i = 0, len = keys.length; i < len; i++) {
-        key = keys[i];
+        const key = keys[i];
         if (!preservedKeys[key]) data[key] = info[key];
       }
 
@@ -183,21 +182,16 @@ module.exports = ctx => {
     }
 
     // TODO: Better post searching
-    const posts = Post.toArray();
-    let post;
-
-    for (let i = 0, len = posts.length; i < len; i++) {
-      post = posts[i];
-
-      if (file.source.startsWith(post.asset_dir)) {
-        return PostAsset.save({
-          _id: id,
-          slug: file.source.substring(post.asset_dir.length),
-          post: post._id,
-          modified: file.type !== 'skip',
-          renderable: file.params.renderable
-        });
-      }
+    const post = Post.toArray().find(post => file.source.startsWith(post.asset_dir));
+
+    if (post != null) {
+      return PostAsset.save({
+        _id: id,
+        slug: file.source.substring(post.asset_dir.length),
+        post: post._id,
+        modified: file.type !== 'skip',
+        renderable: file.params.renderable
+      });
     }
 
     if (doc) {
diff --git a/lib/plugins/tag/asset_img.js b/lib/plugins/tag/asset_img.js
index 7525e7df38..752d0deb05 100644
--- a/lib/plugins/tag/asset_img.js
+++ b/lib/plugins/tag/asset_img.js
@@ -13,22 +13,15 @@ module.exports = ctx => {
   const PostAsset = ctx.model('PostAsset');
 
   return function assetImgTag(args) {
-    let asset;
-    let item = '';
-    let i = 0;
     const len = args.length;
 
     // Find image URL
-    for (; i < len; i++) {
-      item = args[i];
-      asset = PostAsset.findOne({post: this._id, slug: item});
-      if (asset) break;
+    for (let i = 0; i < len; i++) {
+      const asset = PostAsset.findOne({post: this._id, slug: args[i]});
+      if (asset) {
+        args[i] = url.resolve('/', asset.path);
+        return img(ctx)(args);
+      }
     }
-
-    if (!asset) return;
-
-    args[i] = url.resolve('/', asset.path);
-
-    return img(ctx)(args);
   };
 };
diff --git a/lib/plugins/tag/img.js b/lib/plugins/tag/img.js
index 52e8e333dc..99aeccf7b9 100644
--- a/lib/plugins/tag/img.js
+++ b/lib/plugins/tag/img.js
@@ -32,36 +32,24 @@ module.exports = ctx => {
   }
 
   return function imgTag(args, content) {
-
     const classes = [];
-    let meta = '';
-    let width, height, title, alt, src;
-    let item = '';
-    let i = 0;
-    const len = args.length;
+    let src;
 
     // Find image URL and class name
-    for (; i < len; i++) {
-      item = args[i];
-
-      if (rUrl.test(item)) {
+    while (args.length > 0) {
+      const item = args.shift();
+      if (rUrl.test(item) || item[0] === '/') {
         src = makeUrl(item);
         break;
       } else {
-        if (item[0] === '/') {
-          src = makeUrl(item);
-          break;
-        } else {
-          classes.push(item);
-        }
+        classes.push(item);
       }
     }
 
-    // Delete image URL and class name from arguments
-    args = args.slice(i + 1);
+    let width, height, title, alt;
 
     // Find image width and height
-    if (args.length) {
+    if (args && args.length) {
       if (!/\D+/.test(args[0])) {
         width = args.shift();
 
@@ -70,14 +58,13 @@ module.exports = ctx => {
         }
       }
 
-      meta = args.join(' ');
-    }
+      const match = rMeta.exec(args.join(' '));
 
-    // Find image title and alt
-    if (meta && rMeta.test(meta)) {
-      const match = meta.match(rMeta);
-      title = match[1];
-      alt = match[2];
+      // Find image title and alt
+      if (match != null) {
+        title = match[1];
+        alt = match[2];
+      }
     }
 
     const attrs = {
diff --git a/lib/plugins/tag/link.js b/lib/plugins/tag/link.js
index b18f8109de..744f874f88 100644
--- a/lib/plugins/tag/link.js
+++ b/lib/plugins/tag/link.js
@@ -16,13 +16,12 @@ function linkTag(args, content) {
   const text = [];
   let external = false;
   let title = '';
-  let item = '';
   let i = 0;
   const len = args.length;
 
   // Find link URL and text
   for (; i < len; i++) {
-    item = args[i];
+    const item = args[i];
 
     if (rUrl.test(item)) {
       url = item;
diff --git a/lib/plugins/tag/pullquote.js b/lib/plugins/tag/pullquote.js
index c3c347689b..8a2f945d4a 100644
--- a/lib/plugins/tag/pullquote.js
+++ b/lib/plugins/tag/pullquote.js
@@ -9,13 +9,9 @@
 *   {% endpullquote %}
 */
 module.exports = ctx => function pullquoteTag(args, content) {
-  let result = '';
-
   args.unshift('pullquote');
 
-  result += `<blockquote class="${args.join(' ')}">`;
-  result += ctx.render.renderSync({text: content, engine: 'markdown'});
-  result += '</blockquote>';
+  const result = ctx.render.renderSync({text: content, engine: 'markdown'});
 
-  return result;
+  return `<blockquote class="${args.join(' ')}">${result}</blockquote>`;
 };
diff --git a/lib/theme/view.js b/lib/theme/view.js
index ee67c95965..3e96b5818f 100644
--- a/lib/theme/view.js
+++ b/lib/theme/view.js
@@ -70,10 +70,9 @@ View.prototype._buildLocals = function(locals) {
 View.prototype._bindHelpers = function(locals) {
   const helpers = this._helper.list();
   const keys = Object.keys(helpers);
-  let key = '';
 
   for (let i = 0, len = keys.length; i < len; i++) {
-    key = keys[i];
+    const key = keys[i];
     locals[key] = helpers[key].bind(locals);
   }